Henslow’s Sparrow Evaluation

COSSARO Candidate Species at Risk Evaluation for Henslow’s Sparrow (Ammodramus henslowii)

Committee on the Status of Species at Risk in Ontario (COSSARO) Assessed by COSSARO as Endangered

May 2011

Final

Part 1 - COSSARO Candidate species at risk evaluation

May 2011

Henslow’s Sparrow (Ammodramus henslowii)

1.1 Current status and distribution

Current designations:

GRANK – G4 (website checked 22 May 2011).

NRANK Canada – N1B (website checked 22 May 2011).

COSEWIC – Endangered (May 2011) (website checked 22 May 2011). SARA – Endangered (Schedule 1) (website checked 22 May 2011). ESA 2007 – Endangered (Schedule 2) (website checked 22 May 2011).

SRANK – SHB [historical breeder, with potential to be discovered again; also, no consistent breeding sites, although it may appear sporadically for brief periods in attempts to breed] (website checked 22 May 2011).

Distribution in Ontario:

In Ontario, the Henslow’s Sparrow has bred in scattered locations throughout the southern part of the province, in the Mixedwood Plains Ecozone. In recent times, it has been only a sporadic breeder in the province, rarely appearing for more than a year at a time at any breeding site; hence, its status ranking as SHB by the Natural Heritage Information Centre. At present, it appears that the Ontario population can be maintained or recovered only through annual immigration from the U.S.A. (COSEWIC 2011).

Distribution and status outside Ontario:

The Henslow’s Sparrow occurs as a breeding species in tallgrass prairies, wet grasslands, and reclaimed surface mines from Minnesota and New York south to Oklahoma and Tennessee. It has also bred in southwestern Quebec. It is a short- distance migrant, and winters in the southeastern U.S.A., from North Carolina and Arkansas to Florida and Texas (Herkert et al. 2002).

Part 2 - Eligibility for Ontario status assessment

2.1 Application of eligibility criteria

Taxonomic distinctness

Yes. There is no taxonomic dispute about the distinctness of this species. The nominate subspecies is the only one that occurs in Canada. The validity of a second subspecies, which is restricted to the Atlantic slope, and does not occur in Canada, is in question (COSEWIC 2011).

Designatable Units

There is a single designatable unit in Ontario. All recent territorial males or attempts to breed have occurred within a single ecozone, the Mixedwood Plains Ecozone.

Native status

Yes. There is no evidence that the species is not native to Ontario. The Ontario portion of its range is contiguous with the remainder of its range in the U.S.A. A gradual range expansion apparently occurred between 1860 and 1915, filling the gap between Midwestern and east coast populations. This likely was due to forest clearing and the creation of suitable habitat (Herkert et al. 2002).

Presence/absence

Present. The Henslow’s Sparrow occurs in Ontario each year, although post-migration records are quite sporadic. In some years, one or a few birds are found singing on territory in scattered locations, but rarely are birds found during the breeding season in the same location in subsequent years. Since birds are present each year, it cannot be considered extirpated, even though their breeding status is uncertain (breeding confirmation is difficult; only 13 nests have ever been found in Ontario; COSEWIC 2011).

2.2 Eligibility results

1. The putative taxon or DU is valid. Yes
2. The taxon or DU is native to Ontario. Yes
3. The taxon or DU is present in Ontario. Present

Part 3 - Ontario status based on COSSARO evaluation criteria

3.1 Application of primary criteria (rarity and declines)

1. Global rank

Not in any category. G4.

2. Global decline

Endangered. North America-wide Breeding Bird Survey trends show an annual decline of 8.1%/year over the period 1966-2007 (Sauer et al. 2008), for an overall decline of 97%. The Henslow’s Sparrow is considered to be one of the fastest declining songbirds on the continent (NatureServe 2010). The severe decline is due primarily to habitat loss and degradation. However, it should be noted that a recent increasing trend has been found in the American population (see COSEWIC 2011), which is attributed, in part, to the increasing amount of habitat created by coal mine reclamation and the Conservation Reserve Program (an incentive program for farmers to leave their lands uncultivated) (COSEWIC 2011).

3. Northeastern North America ranks

Threatened. Henslow’s Sparrow is listed as S1, S2, SH, or SX in 13 of 22 northeastern North American jurisdictions (59%). For this assessment, only breeding ranks were used (e.g., S1B).

4. Northeastern North America Decline

Endangered. Although there is no specific trend assessment for the northeast as a whole, all of the adjacent jurisdictions (Michigan, New York, Ohio, Pennsylvania, Wisconsin) have undergone declines at least as severe as the overall North American (global) decline noted above (see COSEWIC 2011; Sauer et al. 2008). Only Ohio has shown a recent increase among these states, but the long-term trend there is still one of decline.

5. Ontario occurrences

Endangered. In the recent past, in any given year, there are few (1 or 2 singing males) or no birds present on breeding territories in the province. The species formerly was more widespread, but never frequent. The Natural Heritage Information Centre records 73 element occurrences, 16 of which are considered to extirpated, and 51 of which are historical, leaving 6 relatively recent (within the past 20 years) occurrences, none of which are ranked as high-quality occurrences (NHIC Biodiversity Explorer 2010).

6. Ontario decline

Endangered. The highest recorded number of birds in Ontario in relatively recent times was 25-29 singing males recorded at 13 sites, in 1983. Extensive surveys of known sites and suitable habitat in 1992-1993 found a single bird in each of those years. It has not been found on a Breeding Bird Survey route in the province since 2002. During the 10-year period 2000-2009, it was reported from a total of 16 sites (including Breeding Bird Atlas reports). Most of these records are of single males singing on a single day at a location, with no subsequent occurrence, either in the same year or in following years. The species was found in only nine 10 x 10 km squares in the second Breeding Bird Atlas (2001-2005) compared with 38 squares in the first Breeding Bird Atlas (1981-1985) (80% decline in number of squares). For all intents and purposes, the population of this species in Ontario in recent years has been barely above 0, and there has been no positive evidence of reproductive success, although confirmation of breeding is difficult (note that only 13 nests have ever been found in Ontario, despite its occurrence in the province for a century or so; COSEWIC 2011).

7. Ontario’s conservation responsibility

Not in any category. Ontario’s portion of the global range of Henslow’s Sparrow is much less than 10%, and its proportion of the global population is less than 1%.

3.2 Application of secondary criteria (threats and vulnerability)

1. Population sustainability

Endangered. Although no population viability analysis has been conducted, there is no evidence that any offspring have been produced in Ontario for several decades. Most records of the species outside of migration involve single males singing in suitable habitat. There are few reports of these males being paired, let alone producing young. The most recent report of a pair of birds is from 2005 in Chatham-Kent R.M. (COSEWIC 2011).

2. Lack of regulatory protection for exploited wild populations

Not in any category. Henslow’s Sparrow is protected by the federal Migratory Birds Convention Act and the Species at Risk Act, and by the provincial Endangered Species Act.

3. Direct threats

Endangered. Habitat loss through urbanization, successional change from grassland to shrubland and forest, and conversion of pastures and hay crops to more intensive row-crop agriculture are the primary threats. Drainage of low, wet areas in otherwise suitable grasslands also is a threat, since this species prefers fields that have moist areas within them. Early cutting of hay may also have a negative effect on productivity in this species (NatureServe 2010).

4. Specialized life history or habitat-use characteristics

Endangered. Henslow’s Sparrow is loosely colonial (an unusual trait in grassland sparrows), and in populations with multiple territories, the territories are non-overlapping (Herkert et al. 2002). It is rarely encountered in grassland tracts less than 100 ha in size (NatureServe 2010). It likely utilized provincially rare tallgrass prairies in the past (as it does in the Midwestern part of its current range; Herkert et al. 2002).

3.3 COSSARO evaluation results (primary/secondary)

1. Criteria satisfied in each status category

Number of primary and secondary criteria met in each status category:

Endangered – [4/3]
Threatened – [1/0]
Special concern – [0/0]

Number of Ontario-specific criteria met in each status category:

Endangered – [2]
Threatened – [0]
Special concern – [0]

2. Data deficiency

No.

Recommended status

The application of COSSARO evaluation criteria suggests that Henslow’s Sparrow is Endangered in Ontario.

Part 4 - Ontario status based on COSEWIC evaluation criteria

4.1 Application of cosewic criteria

Regional (Ontario) cosewic criteria assessment

Criterion A – decline in total number of mature individuals

Endangered (A2a,b,c). Estimates based on numbers of atlas squares occupied between the two Ontario Breeding Bird Atlases show an 80% decline over 20 years (55% decline over 10 years). No birds have been detected on Breeding Bird Survey routes in Ontario since 2002. In most recent years, between 0 and 2 birds are found during the breeding season. Habitat suitability continues to decline.

Criterion B – Small distribution range and decline or fluctuation

Endangered (B2a,b). Index of Area of Occupancy estimated at < 100 km² (COSEWIC 2011); in a given year, fewer than 5 occurrences; continuing decline in suitable habitat.

Criterion C – Small and declining number of mature individuals

Endangered (C2ai). Population probably less than 10 in any year.

Criterion D – Very small or restricted total population

Endangered (D). See C above.

Criterion E – Quantitative analysis

Insufficient information. No population viability analysis has been conducted, although for such a small population, it is hardly needed. The population appears to be maintained only by immigration. No evidence of recruitment has been found for several decades.

Rescue Effect

Yes. It appears that the only way in which a population persists in the province is through immigration from the U.S.A. each year. However, populations of this species in adjacent jurisdictions also have declined severely, although a modest increase has occurred in Ohio in the past decade, and birds are occupying newly created habitats in Pennsylvania and elsewhere (reclaimed coal mine spoils) (COSEWIC 2011). Thus, especially if populations in the adjacent states of Ohio and Pennsylvania continue to recover, the possibility of rescue continues to exist.

4.2 COSEWIC Evaluation results

1. Criteria satisfied in each status category

Indicate whether or not a criterion is satisfied in each of the status categories.

Endangered – [yes]
Threatened – [no]
Special concern – [no]

2. Data deficiency

No.

3. Status based on COSEWIC evaluation criteria

The application of COSEWIC evaluation criteria suggests that Henslow’s Sparrow is Endangered in Ontario.

Part 5 - Ontario status determination

5.1 Application of COSSARO and COSEWIC criteria

COSSARO and COSEWIC criteria give the same result. Yes

5.2 Summary of status evaluation

Henslow’s Sparrow is classified as Endangered in Ontario.

The Henslow’s Sparrow formerly occurred in scattered locations in extensive grasslands with moist depressions throughout the Mixedwood Plains Ecozone in southern Ontario, but it now occurs only sporadically in the province. It is found during migration almost every year, but breeding or even territorial records are exceedingly rare, and birds are rarely found during the breeding season in a given location for more than one year in row. It has also bred in southwestern Quebec, but its main range is in the Midwestern U.S. states, from Minnesota and New York south to Oklahoma and Tennessee during the breeding season, and the southeastern states in winter. It is one of the fastest declining songbirds in North America, although small increases have been noted on retired agricultural lands and reclaimed surface mines in Ohio and Pennsylvania. The major threats to this species relate to the loss of extensive grasslands and pasture lands, through urbanization, conversion to more intensive agricultural practices, succession of pastures to shrublands and forests, and perhaps also to drainage of moist areas within existing grasslands and pastures. Early hay cutting also can be detrimental to productivity of this sparrow. The Henslow’s Sparrow is Endangered in Ontario because of the severe declines in populations that has occurred, as well as continuing threats to its habitat.

Information Sources

Literature cited

COSEWIC. 2011. COSEWIC status report on Henslow’s Sparrow, Ammodramus henslowii in Canada. Committee on the Status of Endangered Wildlife in Canada, Ottawa. ix + 37 pp.

Herkert, J. R., P. D. Vickery, and D. E. Kroodsma. 2002. Henslow’s Sparrow (Ammodramus henslowii), The Birds of North America Online (A. Poole, ed.). Cornell Laboratory of Ornithology, Ithaca, New York.

NatureServe Explorer. 2010. NatureServe Explorer: An Online Encyclopedia of Life, Comprehensive Report – Ammodramus henslowii.

NHIC Biodiversity Explorer. 2010. Species report for Ammodramus henslowii (Henslow’s Sparrow). Natural Heritage Information Centre, OMNR, Peterborough. https://www.biodiversityexplorer.mnr.gov.on.ca/nhicWEB/speciesDetailReport.do?elID=180455 [link no longer active]

Sauer, J. R., J. E. Hines, and J. Fallon. 2008. The North American Breeding Bird Survey, Results and Analysis 1966-2007. United States Geological Survey, Patuxtent Wildlife Research Center, Laurel, MD

2. Community and Aboriginal traditional knowledge sources

None

Appendix 1

Northeastern North America rank, status and decline

Occurs as a native species in 22 of 29 northeastern jurisdictions

S-rank or equivalent information available for 22 of 22 jurisdictions = (100%)

S1, S2, SH, or SX in 13 of 22 = (59%)