Baird's Sparrow Status Assessment and Conservation Plan
TABLE OF CONTENTS
POPULATION ESTIMATES AND TRENDS
Breeding Bird Survey
Christmas Bird Count
Breeding season habitat requirements
Winter habitat requirements 15
Disease or Predation
Inadequacy of existing regulatory mechanisms
Other natural and manmade factors
ASSESSMENT AND RECOMMENDATION
Recommendation on current status
Appendix A. State and Provincial Summaries of Baird's Sparrows Status
Appendix B. Summary of Habitat and Management Guidelines
Appendix C. List of Baird's Sparrow Conservation Plan Reviewers,
Individuals and Agencies Contacted
1. Summary of legal and natural history status of Baird's Sparrow throughout its range.
2. Linear measurements (mm) of Baird's Sparrow.
3. Measurements and mass of males from North Dakota (Green 1992).
4. Trends in average percent change per year for Baird's Sparrow from Breeding Bird Survey data from 1966-1996 (Sauer et al 1997).
1. Breeding and wintering distributions of Baird's Sparrow.
2. Examples of Baird's Sparrow's yearly population fluctuations using data from Breeding Bird Survey 1985-1987. Core populations remain fairly stable but other portions of the range show a wide change of densities (J.R. Sauer, written commun,).
3. Summer distribution map for Baird's Sparrow from Breeding Bird Survey 1966-1996, in the average relative abundance of the individuals detected per route per year (Sauer et al. 1996).
4. Annual population trend estimates for Baird's Sparrow from Breeding Bird Survey 1966-1996, individuals detected per route per year(Sauer et al. 1996).
Baird's Sparrow (Ammodramus bairdii) is a grassland specialist endemic to the northern Great Plains. Its behavior and ecology have been shaped by the historical conditions of the Great Plains and the health of its populations are dependent on the conditions of native prairie. Populations of many grassland birds, including Baird's Sparrow, have experienced dramatic declines due to the diminution and deterioration of native grasslands. Further population declines are likely to continue unless efforts are made to end the destruction of native prairie and to properly manage grasslands. Without a new emphasis on prairie management, Baird's Sparrow and other prairie specialists could ultimately be considered for listing under the Endangered Species Act.
Baird's Sparrows have had apparent declines in their populations since their discovery and further significant declines were documented by the Breeding Bird Survey between 1966-1979. The breeding distribution has remained primarily the same since 1844, except it is now largely missing from its eastern margins in Minnesota and Manitoba. These declines resulted in Baird's Sparrow being proposed for listing under the Endangered Species Act in the United States and under the Committee on the Status of Endangered Wildlife in Canada. In 1991, the United States determined that there was not enough data to make a recommendation. In 1997, Baird's Sparrow was re-proposed for listing as threatened in the United States. In 1989, Canada designated Baird's Sparrow as a threatened species and completed a recovery plan in 1993. In 1996, the species was delisted in Canada, primarily due to population estimates in Saskatchewan. The declines documented by the BBS have leveled off since 1980, and trends have remained stable or increasing between 1980-1997.
Habitat loss, mainly through the conversion of native prairie and grasslands to agriculture continues to be the primary threat to Baird's Sparrow populations. Modern agriculture practices, such as haying, mowing, and plowing can result in reproductive failures. High intensity and long duration grazing can also negatively affect Baird's Sparrow populations. The expansion of exotic vegetation in the grasslands and increasing predation and parasitism rates are also threats to Baird's Sparrow populations.
Baird's Sparrows show little site fidelity between years, shifting their populations within the northern Great Plains, primarily in response to fluctuating climatic, and therefore grassland, condition. This nomadism has to some degree hampered a clear assessment of population status of the species that has also been confounded by a lack of standardization or coordination in survey and habitat assessment methods in different geographic portions of their range. Little data are available from wintering grounds.
Although Baird's Sparrow experienced major historical declines with the conversion of native prairie to agriculture, population trend data is currently stable. Current population estimates for most states and provinces in the breeding range are unknown, variable, or controversial; however, many populations are higher than originally thought. There is no question that Baird's Sparrows are adversely affected by the conversion of native prairie to cropland. The greatest needs are for assessment of population and trends, reproduction from marginal habitats and the determination of the effects of various management activities in different portions of the Baird's Sparrow's range.
We especially thank the authors of the State and Provincial summaries for researching and providing details on Baird's Sparrows in their areas. Special thanks to Bill Howe, who thoroughly reviewed the scattered literature and records of occurrence for Baird's Sparrows on the wintering grounds; Brenda Dale who contributed an invaluable and thorough review of the literature on habitat requirements and effects of various management practices on Baird's Sparrows; Stephen Davis who allowed us to use his new data on nesting and reproduction and who thoroughly and heroically reviewed this document more than once; Joanne Munro for the range map; and Caleb Gorden who contributed his knowledge of Baird's Sparrow wintering natural history. The overall content of these summaries and appendices remain as submitted in most cases. However, we have edited and altered the original submissions to various degrees, and take responsibility for any errors found in those summaries, as well as in the body of the report.
We thank all the biologists who attended the two meetings, researchers and reviewers for their contributions and reviews of earlier versions of this document, including O. Bray, J. Bradley, D. Buckland, D. Casey, J.E. Cornely, B.C. Dale, S.K. Davis, K.D. De Smet, J.S. Dieni, D.C. Duncan, D. Flath, G.R. Geupel, J.P. Goossen, C. Gordon, P. Gouse, T. Grant, T. Gutzke, L. Hanebury, W. Howe, S.N.G. Howell, L. Igl, D.H. Johnson, N. McPhillips, R. Murphy, L. Nordstrom, L. Osbourne, D.F. Prellwitz, D. Prescott, J. Price, J. Reichel, D. Searls, J.R. Sauer, D. Sullivan, M. Williams, and M. Winter.
For assistance with quantifying winter distribution and abundance, information on local status, current research, and winter ecology of Baird's Sparrows we thank: C. Black, T. Corman, S. Droege, C. Gordon, J. Grzybowski, A. Henry, D. Krueper, G. Lasley, D. Leal, B. Maynard, R. Meyer, Colorado Bird Observatory (M. Carter; T. Leukering), C. Sexton, J. Whetstone, and S. O. Williams III. Museums contributing specimen data: Acad. of Nat. Sciences, Philadel.; Dept. Ornith., Am. Mus. of Nat. Hist.; Louisiana State Univ. Mus. of Nat. Sci.; Moore Lab. of Ornith.; National Mus. of Nat. Hist.; Mus. Verte. Zool., Univ. Calif.; Univ. Ariz. Mus.; Univ. Mich. Mus. Zool.; Univ. Kansas Mus.; West. Found. of Verte. Zool.; Univ. New Mex. Mus.; Southwest. Col. Nat. Hist. Mus.; Cornell Univ. Dept. of Ecology and Systematics.
This report is dedicated to two Montana ornithologists: Jim Reichel (Montana Natural Heritage Program) and Phil Wright (University of Montana). With their passing, we have lost a wealth of knowledge about Montana birds and two good friends; they are missed.
Finally, we would like to acknowledge the sparrow itself, which captures the imaginations of many, delights with its song, amazes with its secrecy, and instills a sense of concern for an ecosystem that it needs and that needs it. It is our intent that this document summarizes the current status of Baird's Sparrows. Furthermore, it is our hope that the information herein will stimulate further research into effective management techniques and its natural history throughout its range.
BAIRD'S SPARROW (Ammodramus bairdii) STATUS ASSESSMENT AND CONSERVATION PLAN
Common Name: Baird's Sparrow
Scientific name: Ammodramus bairdii Audubon
There are no unsettled taxonomic issues. Originally known as Emberiza bairdii Audubon 1844, its closest relative appears to be Henslow's Sparrow (Ammodramus henslowii) (Zink and Avise 1990). There are no subspecies designated (AOU 1957). The type specimen was collected near Old Fort Union, North Dakota in 1843.
United States: Baird's Sparrow was proposed for listing under the Endangered Species Act (ESA), and the U. S. Fish and Wildlife Service (USFWS) determined that there was not enough data available to make a recommendation at that time (USFWS 1991). It was again proposed for listing in 1997 (Biodiversity Legal Foundation 1997). This document is a review of the available data and data needs. Baird's Sparrow is also considered a "Species of Special Concern/Watch List Species" by "Partner's in Flight" and National Audubon Society (Carter et al. 1996) and a "Species of Management Concern" by the USFWS Migratory Bird Management Office in 1987 and 1995 (USFWS 1995). The Nature Conservancy has assigned it a global rank of rare to widespread and of long-term concern (G4/G3), because of its limited range (M. Morrison, 1995, written commun.).
Canada: In 1989, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) listed it as Threatened. A recovery plan for Canada was published in 1993 (Goossen et al. 1993). In May 1996, COSEWIC removed it from the list, primarily due to large population estimates from Saskatchewan (Skeel, et al. 1995, COSEWIC 1996).
Mexico: No legal status.
Table 1 is a summary of the legal status of Baird's Sparrow in the all the states and provinces where it occurs and Appendix A has details of its status in these state and provinces.
Baird's Sparrow is a small, brown, streaked oscine, similar to the closely related Savannah Sparrow (Passerculus sandwichensis) and Grasshopper Sparrow (Ammodramus savannarum). Average body mass of breeding males from North Dakota is 19.1 g (SD = +1.0; range = 17.0-21.3 g; n = 65; MTG). Tables 2 and 3 show the linear and mass measurements from study skins and live birds.
Baird's Sparrow has a tan, buff, or tinged yellowish (ochre) face, with a prominent dark spot on the upper rear of the ear coverts, near the end of an otherwise tan superciliary. Additionally it has dark-tipped ear coverts and a dark moustache; these form three dark spots making an incomplete semi-circle around the ear coverts. The upper collar is unstreaked and whitish-tan, which accentuates the dark spots, while the lower collar is streaked, merging with streaking on the upper breast. The median stripe is orangish-ochre blending into a light-tan and finely streaked nape, and bordered by dark brown crown stripes which divide toward the nape. The throat is whitish bordered by blackish-brown whiskers that are narrow and short on some birds, but more prominent and wider toward base on others (Godfrey 1986). The upper breast is lightly streaked with narrow, short streaks, which coalesce into a diffuse central spot on some birds. The mid- and lower-breast is unstreaked, from light tan to whitish; the streaked flanks are often covered by the wings while at rest. The back is streaked overall with dark-brown and whitish-cream, which results from the scapulars, rump, tertials, and back feathers having dark brown centers, bordered by chestnut and a wider light tan or whitish margin. The shoulder (lesser upper secondary coverts) is tan-brown and the greater upper, and median upper secondary coverts are tan with expanding dark brown center toward tip, forming two incomplete dark wing bars. The tan edge to otherwise brownish gray primaries give the wings a tan look overall when at rest. The tail feathers are brownish gray with narrow cream-white edge, that is noticeable in flight and on perching birds. The tail is only mildly notched (Godfrey 1986, Howell and Webb 1995, MTG).
The females and males are similar; however, on average the females tend to be slightly more streaked than males on upper breast, and less noticeably colored on the crown and face than males (W. Godfrey, pers. commun., MTG).
The songs of Baird's Sparrows are composed of a series of quick, clear introductory notes followed by a trilled ending; some songs lack a trill. Each male sings only one song of about 15 different song types recorded for the species (Green 1992). These song types are not regionally distinct, but are distributed throughout the range. There are several types of call notes, perhaps the most commonly heard being a rather thick chip; other calls include a high, thin 'seep' note, a series of upslurred tonal notes, twittering that sometimes ends with a rapid series of 'deer' notes, and harsh calls uttered when under stress.
Baird's Sparrows were historically common throughout the Dakotas (Coues 1878) and are currently common in native prairie in the Missouri Coteau region of North Dakota (Stewart 1975; Figure 1). Their present range extends from southeastern Alberta to northwestern Iowa, from east of the Missouri and Yellowstone rivers and extending through northwestern and central North Dakota, into south-central South Dakota (AOU 1983) where they are rare to uncommon (Peterson 1995). In the shorter, drier grasslands west of the Missouri and Yellowstone rivers Baird's Sparrows are uncommon and rare (Stewart 1975). They are uncommon in the grasslands of the eastern and north-central portion of Montana, but common in the northeastern corner (Ellis et al. 1996). Formerly a common breeder in northwestern Minnesota in the 1920's, Baird's Sparrows are now greatly reduced in number and limited to one area of native prairie in Grand Forks County (Janssen 1987, Coffin and Pfannmuller 1988).Baird's Sparrows commonly breed in southeastern Alberta, through southern Saskatchewan, and into
|Table 1. Summary of legal and natural
history status of Baird's Sparrow throughout its range.
Natural Heritage Rankings: G=Global; S=State; B=breeding; N=nonbreeding; Z=zero occurrences; U=unrankable; A=accidental; ?=not ranked; 1=critically imperiled; 2=imperiled; 3=rare and uncommon; 4=widespread.
|State/Province||Status||Legal Status||Natural Heritage Rank|
|UNITED STATES||Regular breeder/winter resident||No designation||G3/G4|
|Colorado, Kansas, Nebraska,
|Regular Migrant||No designations||SZN,SN,S?|
|Montana||Regular breeder||Species of Special Concern||S3S4B, SZN|
|New Mexico||Winter Resident||Threatened||S2N|
|North Dakota||Regular breeder||No designation||SU|
|South Dakota||Regular breeder||No designation||S2B, SZN|
|Texas||Winter Resident||No designation||S2|
|CANADA||Regular breeder||No designation|
|Alberta||Regular breeder||Red List species||S4B?|
|Saskatchewan||Regular breeder||No designation||S3B, SZN|
|MEXICO||Winter Resident||No designation|
|Chihuahua||Winter Resident||No designation||N/A|
|Coahuila||Winter Resident||No designation||N/A|
|Durango||Winter Resident||No designation||N/A|
|Sonora||Winter Resident||No designation||N/A|
|Table 2. Linear measurements (mm) of Baird's Sparrow. Data shown as mean + SD (range; n). Museum study skins from the Museum of Vertebrate Zoology, U.C. Berkeley, n = 11.|
|Measurement||Adult Males||Adult Females|
|Total Length||121.1 + 7.4 (115.9-126.3; 2)||128.4 + 3.8 (122.1-134.1; 7)|
|Wing Chord||65.5 + 6.2 (62.5-68.5; 2)||69.5 + 2.7 (66.0-75.0; 7)|
|Rectrices||50.0 + 4.8 (48.0-52.0; 2)||53.4 + 1.9 (50.0-56.0; 7)|
|Tarsus||20.56 + 1.77 (19.73-21.38; 2)||19.79 + 1.99 (17.49-23.85; 7)|
|Middle Toe||13.56 + 2.18 (12.01-15.1; 2)||14.56 + 1.27 (13.73-16.22; 5)|
|Exposed Culmen||9.12 + 1.32 (8.89-9.34; 2)||9.04 + 0.64 (8.15-9.94; 7)|
|Culmen Depth||5.88 + 0.24 (5.71-6.05; 2)||6.35 + 0.48 (5.91-7.52; 7)|
|Table 3. Measurements and mass of males from North Dakota (Green 1992).|
|Wing Chord (mm)||70.0||2.0||66.0||74.0||93|
|Tail length (mm)||50.0||2.0||43.0||56.0||91|
southwestern Manitoba, loosely bounded by the Aspen Parkland physiographic region to the north and east, and by the Rocky Mountain forests to the west (Godfrey 1986), although Baird's Sparrows can be found in low numbers in the Aspen Parkland Region of Saskatchewan (Davis et. al 1996).
Baird's Sparrows are found in all prairie states (AOU 1957, 1983), including Kansas (Thompson and Ely 1992), Oklahoma (Sutton 1967), eastern Wyoming (Oakleaf et al. 1992) and eastern Colorado (Andrews and Righter 1992). There are a few, mostly unverified, records of occurrence for Nebraska (Ducey 1988), Iowa (Dinsmore et al. 1984), northern Wisconsin (Robbins 1991), and Missouri (Robbins & Easteria 1992) and they are usually considered hypothetical, vagrant, or casual in these states. Extralimital records exist for several states, including New York, California, and Maryland (DeSante and Pyle 1986), Illinois (Bohlen 1989), British Columbia (Kautesk 1982), Ontario (Lemey 1981), and West Virginia (Breiding 1985; Appendix A).
Baird's Sparrow wintering range includes the
grasslands of southeastern Arizona, southern New Mexico, and southern Texas in
the United States and northern Mexico in portions of the states of Chihuahua,
Coahuila, Durango, and Sonora (AOU 1983, Howell and Webb 1995; Figure 1).
Baird's Sparrows are thought to migrate as individuals or in small groups. During migration they are quiet, secretive and difficult to see. It is thought that most individuals migrate at night at high altitudes (Thompson and Ely 1992).
They arrive on breeding grounds from early- to mid-May, sometimes as late as early June in the northern extremes of the range (Cartwright et al. 1937). Southward migration begins in August, possibly late-July for some individuals, while some birds may remain on breeding grounds until October (Lane 1968). Records from Arizona and New Mexico indicate that individuals arrive on wintering grounds in early-to mid-August, and some individuals remain as late as mid-May.
Baird's Sparrows earliest documented arrival date is 4 May (Davis and Sealy in press A, L.D. Igl, D.H. Johnson, and H.A. Kantrud, unpubl. data) to as late as the second week of June (Carwright et al. 1937). Baird's Sparrows arrive in Alberta by 10 May (Semenchuk 1991).
They breed in the northern Great Plains from late May to mid-August, with peak activity from early June to late July. Egg laying dates average from June 5 to July 21, but eggs are occasionally laid in late May. Dependent fledglings have been observed as early as June 30 and as late as August 18 (Stewart 1975, Davis and Sealy in press A).
Nests are in a scrape on the ground and made of grasses with occasional strands of horse hair, moss, stems of forbs, or other fine materials (Lane 1968). Nests are hidden in the grass and are usually constructed in depressions or scrapes in the ground, and are overhung by tufts of grass. Nests are always concealed from above and can be difficult to find (Lane 1968, Cartwright et al. 1937, G. Geupel/MTG/SLJ.). Nests in Manitoba averaged 6.2 + 0.1 cm in diameter and 4.6 + 0.1 cm deep (n=64), with 61% of the nests located in scrapes at the base of a clump of a narrow leaf grass species (Davis and Sealy in press A).
Clutch size varies from 3 to 6 eggs, with a mean of 4.7 eggs; 5 is the most common clutch size (Cartwright 1937, Stewart 1975) although 4-egg clutches are frequently observed (Davis and Sealy in press A). The length of incubation is 11-12 days, and young fledge between 8-11 days (Davis and Sealy in press A). Mean egg size is 19.3 + 0.1 mm long by 14.7 + 0.0 mm (range 17.0-21.3 mm long and 13.3-15.6 mm wide, n=251; Davis and Sealy in press A).
In Manitoba, a banded female initiated a second clutch 5-8 days after fledging the first brood (Davis and Sealy in press A). Breeding dates and behaviors of adults indicate that two broods are produced by some pairs in some years (Mahon 1995, MTG/SLJ); however, Lane (1968) believed that second broods were not normally produced.
Fifty percent (n=71) of nests fledged at least one young with a mean of 1.4 + 0.2 young fledged per nest while successful nests fledged an average of 2.8 + 0.2 young per nests (Davis and Sealy in press A). Nest success for Manitoba was 37% with the daily survival rate similar for the nestling and incubation stages (Davis and Sealy in press A); in Montana nest success in 1996 was 57% (n=21; SLJ) for all stages. Nests were an average of 67.9 m (range 6 - 365 m) from the nearest perch at least 1 m high (Davis and Sealy in press A).
Breeding densities from several studies were summarized by Sousa and McDonal (1983). Densities varied from 11.5 pairs/40 ha to 22.5 pairs/ 40 ha for ungrazed, undisturbed prairie in Alberta (Owens and Myres 1973), Saskatchewan (Maher 1979) and North Dakota (Stewart and Kantrud 1972). Densities on grazed sites were reported to be less than 5 pairs/40 ha (Maher 1979; Renken and Dinsmore 1987). Densities on burned sites had significantly more individuals on plots burned 4 times (3.2 males per 16 ha/8 males per 40 ha) than on plots burned 2 times (1.1 males per 16 ha/2.75 males per 40 ha ) between 1970 and 1992 (Winter 1994, Madden 1996). Schmidt (1990) found 10-32 singing males/40 ha at the McIntyre Ranch near McGrath, Alberta. In a 5-year survey at Lostwood National Wildlife Refuge (LNWR) in northwestern North Dakota, 8.5, 30.6, 32.5, 22.6, and 21.2 males/40 ha were found between 1987-1991 (MTG).
Average breeding territory size ranges from 0.68 ha to 1.2 ha, with larger territories reported during the first few weeks of territory establishment (Winter 1994). Territories in sites with the highest densities averaged 1.05 ha (0.89-1.43 ha, n=11), while territories averaged 1.42 ha (1.19-1.75 ha) in less densely inhabited sites (Winter 1994). Lane (1968) reported territory size to range from 0.4-0.8 ha.
There is anecdotal evidence that males prefer to establish territories next to each other, suggesting that the species might be semi-colonial (Winter 1994, MTG/SLJ).
Baird's Sparrow and several other grassland
species are noted for a lack of breeding site fidelity, appearing semi-nomadic
in response to climatic fluctuations (Green 1992, Price 1995). In a 4-year study
at LNWR, only 5% of color-banded breeding males returned to breed at the same
site they occupied the previous year (n=95). Those that returned once (n=5)
appeared to be more likely to return for a third year (n=3), and one returned
for a fourth year (Green 1992). These data, in addition to frequently
significant yearly fluctuations in populations (De Smet and Miller 1989, Lane
1968; Figure 2), and apparent lack of geographical variation in song (Green
1992) indicate a semi-nomadic migratory behavior.
POPULATION ESTIMATES AND TRENDS
The overall breeding distribution of Baird's Sparrows has probably remained basically unchanged since its discovery in 1843 (Coues 1878), except it is now mostly missing from the eastern margins of its historical range in Minnesota and Manitoba (Coffin and Pfannmuller 1988, De Smet and Miller 1989; Figure 3). Population numbers may have been reduced drastically from the 1800's when Coues (1878) called Baird's Sparrows "one of the most abundant species in the Dakota Territory." These population declines are undoubtedly due to conversion of native prairie to agriculture and to modern agricultural practices.
The North Dakota population of Baird's Sparrow was estimated in 1967 (Stewart and Kantrud 1972) and this methodology was repeated in 1992 and 1993 (Igl and Johnson 1997). The average density of Baird's Sparrows was 0.8 pairs/40 ha in 1967 (Stewart and Kantrud 1972) and the estimate of the North Dakota population was 376,000 pairs (95% confidence interval = 208,000-543,000 pairs). In 1992 the same study design yielded a statewide estimate (with 95% confidence interval) of 171,000 pairs (90,000-251,000), and in 1993 the estimate was 279,000 (140,000-418,000) (Igl and Johnson 1997). The distribution of Baird's Sparrows in any given year, like that of other prairie birds, maybe tied to precipitation patterns (Knopf 1994). Thus, the fact that in 1967 typical precipitation was recorded, while 1992 was a dry year and 1993 a wet year may explain some of the variations in densities in North Dakota.
Population estimates in Canada have been derived from various techniques and are probably not directly comparable to each other. The total population of Baird's Sparrows in Alberta was estimated to be 9,300 males (18,600 individuals) (Goossen et al. 1993). The total population in Manitoba was estimated to be 1,700 males (3,400 individuals) (K. De Smet written commun.). The total population of Baird's Sparrow in Saskatchewan for 1994 was estimated to be 0.95 million males (1.9 million individuals; 1.06-3.02 million individuals = 95% confidence limits) from surveys in grassland, hayland, and cropland (Skeel et al. 1995). This population estimate from Saskatchewan was thought to be too high by some reviewers. Criticisms of this study include a nonrandom habitat sampling bias, assumptions made about the distance singing birds were from census takers, and lack of independence in the samples (B. Dale, written commun.). However, it is the most extensive survey to date of Baird's Sparrows in Saskatchewan, and might be the best measure of total population for that Province, until another census is undertaken. Baird's Sparrow populations remain high in portions its range (Schmidt 1990, D. Johnson pers. commun.) and some populations may be larger than previously believed (Skeel et al. 1995). However, local declines continue to occur (Janssen 1987, De Smet ad Miller 1989) and some threats to Baird's Sparrow populations exist in many geographic areas.
During the period of 1966-1979, Baird's Sparrow
showed persistent and steep declines for all areas, except Montana (Table 4).
There was a significant downward trend (in mean annual percent change) in the
continental population documented by the BBS for this period (Sauer et al.
1996). These declines are significant in 46% of the areas analyzed and the
declines for the entire survey were significant (p=0.05) at -4.75 annually, with
a small number of routes ( n=52). These declines occurred in the geographic
areas with one of the largest Baird's Sparrow populations in the northern Great
Plains (Figure 4). De Smet and Miller (1989) suggest that the declines in the
population in prairie Canada during the period 1970-1985, using BBS data, may be
as great as 35-55%. For the period 1980-1996, the trends are level in most
geographic areas, including the entire survey at 1.1 (non-significant; n=95),
and significant increases were noted in the Glaciated Missouri Plateau region
(+3.3; p<0.20; n=41; Table 4). BBS data in some areas are probably too sparse
and variable to accurately determine population trends in many of the
physiographic regions. The average trends over the 30 years (1966-1996) of the
BBS shows Baird's Sparrow population trends to be stable. This trend equals
-1.6, non-significant for n=115 routes (Sauer et. al 1996; Table 4).
Breeding Bird Survey
Monitoring efforts in the United States and
Canada are mainly limited to the BBS. The interpretation of BBS data is limited
by the number and distribution of routes completed in an area and by the
negative roadside bias shown by Baird's Sparrow (Davis et. al 1996). There are
several other ongoing monitoring studies currently being conducted by Canadian
Wildlife Service, Saskatchewan Wetland Conservation Corporation and USFWS
Christmas Bird Count
The Christmas Bird Counts (CBC) in the southern portion of the United States does not cover the Baird's Sparrow range, although they have been recorded during these surveys. Two CBC's that recorded Baird's Sparrows have recently been started in Mexico; but currently there are few monitoring efforts in the southern range (Appendix A).
BAIRD'S SPARROW TREND
Figure 2. Examples of Baird's Sparrow's yearly population fluctuations using data from Breeding Bird Survey. Core populations remain fairly stable but other portions of the range show a wide change of densities (J.R. Sauer, J.Price, written commun,).
|Table 4. Trends in average percent change per year for Baird's Sparrow from Breeding Bird Survey data from 1966-1996 (Sauer et al 1997). P: *=<0.20; **=<0.10; ***=<0.05.|
|Trend %`||P||N||95% CI||Trend %||P||N||Trend %||P||N|
|Glaciated Missouri Plateau||2.8||*||46||-0.9||6.6||-7.4||15||3.3||*||41|
|Great Plains Roughlands||0.0||25||-8.8||8.9||-2.0||13||-3.7||19|
|FWS Region 6||-1.6||48||-6.2||3.0||-4.2||**||21||-1.5||42|
Breeding season habitat requirements
Habitat preferences of Baird's Sparrows on the breeding
grounds are traditionally described as being idle to light-moderately grazed
tracts of native prairie (Cartwright et al. 1937). In northwestern North Dakota,
Baird's Sparrows were most densely populated and had the smallest territories in
grassland with litter up to 2 cm deep, <10% woody cover, relatively high
coverage of forbs (20%), intermediate vegetation with an average height of 23
cm, and with a patchy distribution of forbs, grass and bare soil (Winter 1994;
Appendix B). Litter was significantly deeper inside Baird's Sparrow territories
than outside (1.19 cm vs. 0.87 cm) and sites with shrub cover greater than 25%
are avoided. Baird's Sparrows prefer native grasslands that have a shrub cover
<20%, litter depth >0 and up to 3 or 4 cm deep, and grass height from
10-20 cm or higher (Dale 1983, Sousa and McDonal 1983; Appendix B). The limited
emergent shrubs that are present, both dead or alive, are often used as singing
perches (Cartwright et al. 1937, Lane 1968) although not required since they
sing from the ground, grass clumps, or forbs.
While breeding Baird's Sparrows may prefer native
grasslands, they also occur in hayfields, seeded pastures (Sutter et al. 1995,
Davis et. al 1996), weedy stubble fields and retired croplands (Kantrud and
Kologiski 1983, Stewart 1975, De Smet and Conrad 1989, Davis 1994), wheat fields
(Lane 1968), and in dry wetland basins (Goossen et al. 1993). Appendix B has a
detailed discussion of the habitat requirements of Baird's Sparrow throughout
Baird's Sparrows show a positive association with native grasses and a negative association with smooth brome (Bromus inermis) (Dale et al. 1993, Madden 1996). On Lostwood NWR, brome and other broad-leaved, exotic grasses were significantly less common in areas occupied by Baird's Sparrows compared to unoccupied areas (Madden 1996). Smooth brome is a codominant and increasing in mixed grass prairie on the northern and central Missouri Coteau and much of the northwestern Drift Plain in North Dakota. On xeric, sandy soils it is much less readily established and less able to compete with native, herbaceous flora.
Leafy spurge (Euphorbia esula)
and western snowberry (Symphoricarpos
occidentalis) are exotic species that
are invading native prairie and other untilled uplands in North Dakota. In some
portions of their range, idle native prairie can
gradually become dominated by these species. Both of these species create monotypic stands and conditions that make the
habitat unsuitable for Baird's Sparrows.
The results for crested wheatgrass (Agropyron cristatum) are mixed. Crested wheatgrass may be suitable for Baird's Sparrow since it is structurally similar to native grasses, particularly when grazed or burned (Madden 1996, Davis and Duncan in press). Baird's Sparrows have shown equal or higher densities in comparisons between grazed stands of native grasses and grazed stands of crested wheatgrass in Saskatchewan (Davis and Duncan in press, Skeel et al.1995, Sutter et al. 1995) and Alberta (Mahon 1995). However, idle crested wheatgrass in North Dakota was not attractive to Baird's Sparrow (Johnson and Schwartz 1993), while burned crested wheatgrass was tolerated (Madden 1996).
Some invasion by Kentucky bluegrass (Poa
pratensis) is also accepted (Madden 1996), suggesting that Baird's Sparrows
will use exotic species that are structurally similar to native mixed grass
Baird's Sparrow can be significantly associated with the size of grassland fragment and are an area sensitive species requiring approximately 63 ha (Davis 1998). A decrease in pasture size may also cause increases in parasitism (S. Davis written commun.).
Winter habitat requirements
Little is known about winter range habitat requirements. Baird's Sparrows are consistently seen in areas with dense and expansive grasslands, either solitary or in small numbers with other grassland specialists, including Grasshopper Sparrow and Savannah Sparrow.
Winter habitat relationships and movement patterns of grassland sparrows are the primary objective of an study in southeastern Arizona. Preliminary results suggest that Baird's Sparrows might be sedentary, with fixed winter home ranges within and between years (C. Gordon, written commun.; Appendix A).
Effects of management techniques can vary greatly throughout the range of Baird's Sparrows. Climate, particularly average rainfall, and topography can greatly change the response of grassland vegetation to management techniques. Therefore, it is not always possible to apply the results from a local study across the geographic range. For example, controlled burning intervals could be longer in the northern drier prairie. Grazing might play a bigger role in grassland management in these dry areas than in the wetter portion of the mixed grass prairie. Appendix B is a detailed summary of the habitat requirements of the species and effects of different grassland management techniques on their populations.
Controlled burning offers one management tool for maintaining productive Baird's Sparrow habitat in the Missouri Coteau (Winter 1994, Madden 1996). In northwestern North Dakota, the vegetation characteristics preferred by Baird's Sparrow were more common in study areas burned 4 times, rather than 2 times or not at all between 1970-1992. Generally, populations decline in the first year after the burn, but then increase, reaching peak densities 2 to 4 years after the burn, followed by a decline in density in subsequent years (Winter 1994, Madden 1996, D. Johnson, pers. commun.). In northwestern North Dakota, unburned plots gradually become dominated by western snowberry and by thick, dense grasses that create habitat features avoided by Baird's Sparrows.
Many studies have demonstrated that Baird's Sparrows
can tolerate light to moderate levels of livestock grazing, depending on
duration and intensity of the grazing and the physiographic area (Appendix B).
However, long duration and heavy grazing can result in abandonment of the
Habitat: Baird's Sparrows are grassland specialists endemic to the northern Great Plains. The conversion of native prairie to cropland is the primary threat to Baird's Sparrow populations in breeding areas (Lane 1968, Stewart 1975, Owens and Myres 1973, Goossen et al. 1993). Over-grazing and poor rangeland management also contribute to the loss of Baird's Sparrow habitat (Goossen et al. 1993). Mixed grass prairie has declined 60-99% in acreage in the prairie provinces and North Dakota (Samson and Knopf 1994), with over 90% of the grasslands in Canada converted to agriculture. It is probable that Baird's Sparrow populations will decline in proportion to the conversion of native prairie.
Baird's Sparrow are associated with size of grassland fragments and decreases in pasture size may also cause increases in parasitism. Small fragments of prairie could act as population "sinks" creating declines.
Regulation of Baird's Sparrow populations could also be influenced by factors occurring on the wintering and migration areas. However, we know little about the natural history, habitat, range, and limiting factors of Baird's Sparrow on these areas.
Susceptibility to human disturbance is a factor in Baird's Sparrow distribution. Disturbances caused by plowing, brushing, burning, movement of livestock, grazing, haying, and mowing can result in the abandonment of an area and reproductive failure.
Disease or Predation:
Disease has not been documented as a
Predation can be a cause of reproductive failure in Baird's Sparrows (Davis and Sealy in press B). Predation frequencies ranged from 26% - 46% for nests in southwestern Manitoba (Davis 1994) to 50% - 71% in southern Saskatchewan (Davis 1998). Davis and Sealy (in press B) reported predation by striped skunk (Mephitis mephitis) and thirteen-lined ground squirrel (Citellus tridecemlineatus). Richardson's ground-squirrels (Spermophilus richardsoni) depredated eggs, nestlings, and fledglings at a site in Alberta (Mahon 1995). A weasel was suspected when an adult dead male was found mauled but uneaten near a nest with decapitated young (MTG). Other potential predators include American Crow (Corvus brachyrhyncos), Northern Harrier (Circus cyaneus), and western plains garter snake (Thamnophis radix haydeni) (Davis and Sealy in press B); in general, major predators are probably small mammals, birds, and snakes.
Baird's Sparrow nests are parasitized by Brown-headed Cowbirds (Molothrus ater). Davis and Sealy (in press B) found that 36% of 74 nests in southwestern Manitoba were parasitized with an average of 2 cowbirds eggs (range 1-4). Significantly fewer young were fledged from successful parasitized nests than from successful non-parasitized nests, resulting in an average cost of 1.1 Baird's Sparrow fledglings per parasitized nest. Egg removal by cowbirds was likely the primary cause of lowered productivity in parasitized nests. In Saskatchewan, 32% of 61 Baird's Sparrow nests were parasitized, and 79% of parasitized nests contained more than one cowbird egg (S. Davis written commun,).
Inadequacy of existing regulatory mechanisms: Current regulations appear to provide Baird's Sparrows with adequate protection throughout its breeding range. Baird's Sparrows are protected in under the Migratory Bird Treaty Act (1918) in the United States, the Migratory Bird Convention Act (1916) in Canada and the Convention for the Protection of Migratory Birds and Game Mammals (1936) in Mexico. The ESA in the U.S. and COSEWIC in Canada will provide protection for the species if Baird's Sparrow becomes threatened with extinction. Baird's Sparrow is a USFWS Migratory Nongame Species of Management Concern (USFWS 1995). Baird's Sparrow was a Category 2 candidate for review for possible addition to the Federal endangered or threatened species list (USFWS 1991) until use of the Category 2 list was discontinued (USFWS 1996). Table 1 is a summary of the legal status of the species in states and provinces throughout its range.
No protection for Baird's Sparrow habitat exists for the breeding range in the United States and Canada. Incentive programs such as the Grassland Conservation Program offer some breeding habitat protection in upland easements in perpetuity. Other incentive programs such the Conservation Reserve Program (CRP) do not contribute habitat for Baird's Sparrow (Johnson and Igl 1995) since most cover currently re-seeded under this program is exotic grass or exotic grass/legume mixtures, which are unsuitable for Baird's Sparrow.
Current regulatory mechanisms are inadequate to protect the species and its habitats on the winter range. Mexico has no regulations to protect the habitat of Baird's Sparrow and current regulations protecting the species are not adequately enforced.
Other natural or manmade factors:
Pesticides: Not documented as a threat.
Population size: Conflicting data on population size make this factor difficult to evaluate. Populations are likely to be greater then earlier believed and remain high in many portions of the range.
Burning: Controlled-burning programs that mimic natural fire intervals and help re-create native prairie conditions are preferred by Baird's Sparrow in parts of their range. However, Baird's Sparrow will not use the area in the first year or two after a burn and the interval between burns will vary by region and is critical to a successful program (Appendix B).
Mowing: Baird's Sparrows are absent or sparsely distributed where mowing is greatest but they are sometimes found in stubble fields and fallow land (Bent 1968, Stewart 1975, De Smet and Conrad 1989). Baird's Sparrow nest initiation dates indicate that the July 15 haying date recommended by the North American Wetland Management Plan is too early (Davis et. al 1996; SLJ/MTG).
Grazing: Several studies have noted that Baird's Sparrows are found in moderately grazed native prairie, but are absent or very sparsely distributed where grazing is heavy (Kantrud 1981, Owens and Myres 1973, Stewart 1975, Dale 1983, Samson and Knopf 1994, Mahon 1995). There is evidence that grazed grasslands may support fewer Baird's Sparrows than in ungrazed areas in portions of their range (Owens and Myres 1973, Maher 1979, Dale 1983). Grazing affects vegetation height, percent bare ground, litter depth, and can compact the vegetation and soil. Response of the vegetation used to Baird's Sparrow to grazing varies geographically and with grazing duration and intensity.
Introduced Vegetation: Baird's Sparrow have shown a negative correlation with smooth brome (Dale 1983, Madden 1996). Although the response of Baird's Sparrows to leafy spurge has not been studied, this weed can dominate large patches of grasslands and changes the habitat features apparently critical to Baird's Sparrows. Other noxious species of weeds or exotic grasses could pose serious threats in the future to the long term survival of Baird's Sparrows in native prairie.
ASSESSMENT AND RECOMMENDATIONS
Recommendation on current status
We recommend no change in Baird's Sparrows status at this time. While the species has experienced major declines with European settlement of the prairies and the conversion of native prairie to agriculture, population trend data over the last 15 years show their populations to have become relatively stable. Current population estimates for most states and provinces in the breeding range are unknown and variable, but even the most conservative estimates indicate a large population in parts of the range. There is no question that Baird's Sparrows are adversely affected by the conversion of native prairie to cropland, resulting in a range constriction from the eastern margins of their historical range. Although singing males have been found in cropland and hayfields, their productivity in these habitats and circumstances under which they are used is unknown. Baird's Sparrows are apparently compatible with light grazing and could successfully reproduce in some haylands, but additional comparative studies are recommended to determine Baird's Sparrows tolerance to types and levels of grassland management. Essentially no information is available from the wintering grounds or from migration that would help determine population trends or recommend a change in status. Since threats still exist, Baird's Sparrow should remain a species of special concern and its status monitored.
Baird's Sparrows are a member of a guild of species that are dependent on the health and availability of native grasslands (Knopf 1994). Other grassland species could benefit to some degree from conservation efforts aimed at Baird's Sparrow, although details of their natural history, range, and habitat requirements will vary. Other grassland species include Sprague's Pipit (Anthus spragueii), McCown's Longspur (Calcarius mccownii), Chestnut-collared Longspur (C. ornatus), Western Meadowlark (Sturnella neglecta), Savannah Sparrow, Grasshopper Sparrow, Vesper Sparrow (Pooecetes gramineus), and Burrowing Owl (Athene cunicularia).
The BBS has documented general population declines in Baird's Sparrow and other grassland species of the Great Plains over the past 30 years (Sauer et al. 1996). Long term conservation of Baird's Sparrows and associated species are linked to conservation of the native prairie ecosystem. CRP has contributed relatively little habitat for Baird's Sparrow, although other grassland species have benefitted from this program (Johnson and Igl 1995). In the United States, the only viable approach for the conservation of Baird's Sparrows is to conserve, restore, and actively manage native grasslands or to alter the structure of CRP lands. Due to extensive habitat loss, Baird's Sparrows will probably never recover to historic levels. However, where suitable habitat remains, the proper use and timing of mowing, grazing, and burning, along with restoration efforts where feasible, will be most successful in maintaining viable populations. While it is clear that in certain physiographic areas no active management, or ill-timed use of these management tools, has been detrimental to Baird's Sparrows, they do respond positively to native prairie restoration and will reoccupy formerly unuseable habitats.
Although fewer Baird's Sparrows have been counted in some years and in some areas compared to others, it may be that populations have shifted, in response to local environmental conditions (Figures 2 and 4). This species appears to be semi-nomadic, and might be able to find suitable habitat wherever it exists within the breeding range; however, if these shifts in distribution and abundance are related to weather conditions (Price 1995) then suitable habitat would need to be provided throughout the breeding range to accommodate locally variable weather and habitat conditions. The spatial and temporal dynamics of Baird's Sparrow could make it difficult to set aside or preserve suitable habitat because they may not be found in an area every year; however, in some regions population sizes do not fluctuate, and annual site use is more predictable (Figure 2). Price (1995) used 18 climate variables to predict the response of Baird's Sparrows to climatic change. The two models used for Baird's Sparrows predicted completely opposite results, with one predicting extirpation and the other predicting a range expansion. The future of the Baird's Sparrow populations remain unclear and further work is needed.
1) Since reliable population data are unavailable, a two year range-wide survey, similar to that completed in North Dakota (Stewart and Kantrud 1972, Igl and Johnson 1997) is proposed. Baird's Sparrow nomadism complicates the survey design, but a two year range-wide survey should mitigate the these effects.
2) A better understanding of the minimum preserve or patch size is important for the determination of priority habitats and areas for protection and restoration..
3) Little is known about the Baird's Sparrow's reproductive capability, habitat, and timing. There is little productivity data available; even less is known about survivorship. Currently, there are ongoing productivity studies in Saskatchewan (S.K. Davis and B.C. Dale), Montana (S. L. Jones and F. Prellwitz), and North Dakota (T. Grant and S.L. Jones), but more sites throughout the geographic range are necessary. Of special interest would be comparative studies on the reproductive success of Baird's Sparrows in different habitats: native and non-native grasslands, and cropland. Baird's Sparrow sing in croplands and fallow fields that might share critical structural characteristics with native prairie, but the productivity of these birds has not been investigated.
4) Further investigations on the response of Baird's Sparrows to different management techniques are needed. Current long-term studies in which data are being collected on population sizes, their distribution, and productivity are critical to the evaluation of the status of this species, but further work at different sites in their geographic range are needed.
5) The winter range and habitat use of the Baird's Sparrow needs to be documented. An inventory of wintering areas and an evaluation of their quality and security is needed to assess the influence winter areas are having on Baird's Sparrow populations.
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