COSEWIC assessment and update status report on the Hooded Warbler Wilsonia citrina in Canada (2000)
Table of Contents
COSEWIC status reports are working documents used in assigning the status of wildlife species suspected of being at risk. This report may be cited as follows:
Please note: Persons wishing to cite data in the report should refer to the report (and cite the author(s)); persons wishing to cite the COSEWIC status will refer to the assessment (and cite COSEWIC). A production note will be provided if additional information on the status report history is required.
COSEWIC 2000. COSEWIC assessment and update status report on the Hooded Warbler Wilsonia citrina in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 11 pp.
(http://www.registrelep-sararegistry.gc.ca/sar/assessment/status_e.cfm)
James, R.D. 2000. Update COSEWIC status report on the Hooded Warbler Wilsonia citrina in COSEWIC assessment and update status report on the Hooded Warbler Wilsonia citrina in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 1-11 pp.
Previous Report:
Page, Annette M. and M.D. Cadman. 1994. COSEWIC status report on the Hooded Warbler Wilsonia citrina in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. 19 pp.
Également disponible en français sous le titre Évaluation et Rapport de situation du COSEPAC sur la situation de la Paruline à capuchon (Wilsonia citrina) au Canada – Mise à jour
Cover illustration:
Hooded Warbler -- R.D. James, Gateways Centre, R.R. #3, S1480, Conc. 7, Sunderland, ON, L0C 1H0.
©Minister of Public Works and Government Services Canada, 2002
Catalogue No.CW69-14/11-2002E-IN
ISBN 0-662-32921-X
COSEWIC Assessment Summary
Common name : Hooded Warbler
Scientific name : Wilsonia citrina
Status : Threatened
Reason for designation : This population is small and the quantity and quality of habitat will likely decline in the future. The likelihood of a rescue effect from United States populations is limited by availability of suitable habitat in Canada.
Occurrence : Ontario
Status history : Designated Threatened in April 1994. Status re-examined and confirmed in November 2000. Last assessment based on an update status report.
COSEWIC Executive Summary
Description
This small songbird is olive coloured on the back and bright yellow on the face and under sides. The male has a black hood and throat, while retaining a bright yellow mask and forehead. The eye appears large and the lores are dark. The female usually has only a small amount of black on the crown with little or no black on the throat or sides of the head. In both sexes the tail appears white from below, and olive green above. The white shows above only when the tail is flicked open. Immature males are like adults, except that the black hood feathers are extensively tipped with olive or yellow. Immature females lack black entirely. Some females have a fairly extensive hood, but never as complete as that of males. The birds are about 13 cm long. The song is a loud musical whistled ta-wit ta-wit ta-wit tee-yo. No other warbler has the clearly defined black hood, with bright yellow face and under sides.
Distribution
Hooded Warblers breed over most of the eastern United States, from southern Wisconsin and eastern Texas to the Atlantic coast. In Canada it nests almost entirely in extreme southern Ontario close to Lake Erie. It is a migratory bird that moves to the Caribbean coast of Mexico and central America, plus Cuba, and a few Caribbean islands, and possibly into extreme northwestern South America for the winter. In Ontario it may have been a more widespread nester at one time before forest clearing in the 1800s following European settlement. It has nested north to Georgian Bay in recent times, where a relatively small remnant of forest has survived. It has also summered in the Kingston area. It could have had a continuous range that far north at one time.
Population size and trend
In the eastern United States, it is numerous, widespread and doing well. There has been a slow increase there since 1966, including in Ohio, Pennsylvania, and New York to the immediate south. In Michigan it is in a similar situation to that of Ontario with former declines, but in recent years there appears to have been a slight increase. In Ontario we can only speculate that it was once much more numerous when suitable habitat would have covered much of southern Ontario south of the Canadian Shield. But, it is a deep forest species and may have been largely overlooked in the past. But, the first estimates of numbers present did not come until the breeding bird atlas program of the early 1980s. At that time there were an estimated 25 to 53 pairs only. But because not all habitat was surveyed, the actual population may have been close to 100 pairs. More thorough surveys within a few years, estimated between 80 and 176 pairs. That may not have been an increase, but only a more complete survey. A detailed survey in 1997 at 51 known former breeding sites found 88 pairs, with an estimated total of 145 to 300 pairs. A 1998 survey estimated 144 to 207 pairs. These estimates suggest that the population is also increasing in Canada, and it may have doubled its numbers in the past decade.
Habitat
Hooded Warblers nest in mature hardwood forests with tall trees and a relatively well-closed canopy. They occupy small clearings, such as created by a fallen tree, where a dense growth of low shrubbery has sprung up. They move into such an area one to five years after the clearing has been created and will use it for 10 to 12 years only until the shrubs get too tall. It is area sensitive, requiring large forests of at least 20 to 30 ha, preferably much larger. They are also forest interior dwellers. Predation and parasitism rates are higher near forest edges, making it difficult for this species to survive long in such situations. Large forest tracts are essential to them.
However, in southern Ontario, less than 20% of forest cover remains in most counties, and is only about 6 to 7% in the Carolinian region. Much of this forest is also highly fragmented and in small patches. In the whole of the Carolinian region forest interior covers only about 2% of the land area, and many patches are not large enough to hold a population. While selective logging may create habitat in large tracts for this species, it would have to be repeated every 10 years to be effective. Furthermore, it would have to be very selective to retain a largely unbroken canopy – something that most harvesters would not want to do.
General biology
Young birds mature in one year and return early to territories. Return flights bring the birds back by mid-March to late April. Birds will be singing to attract a single mate soon after settling on a territory. Once paired, the female chooses the nest site, and builds the nest. Nest building is likely to take about one week, and eggs may be laid by early June. The nest is a soft open cup, woven of soft inner bark, fine grasses and plant down, lined with fine grasses. It is placed in a deciduous shrub or sapling close to the ground, usually below 1 m high. The usual clutch is four eggs, laid one per day. Incubation is by the female alone, lasting about 12 days. The altricial young are fed by both male and female, but only the female broods the young for the first few days. Brood parasitism by Brown-headed Cowbirds is high at 47% in Ontario. Nests lost to predators will be replaced, but ordinarily birds in Ontario have only one nesting per year if successful in getting some young out of the nest. Losses to predators may range from 40 to 75%, being least in the largest forest patches.
Young leave the nest after 8 or 9 days, and can fly 2 – 3 days later. Young gradually become independent over a period of 4 to 5 weeks. Each parent will care for half the brood. Life span is typically short, but some may live to be 10 years old. Hooded Warblers eat mainly a variety of insects, which they find on the foliage of shrubs and saplings. This contributes to forest insect suppression.
Individual summer territories may be as small as one hectare, defended by both adults. In wintering areas males and females occupy different habitats, and each defend a small territory. Pairs are monogamous, but typically males wander into adjacent territories where they mate with neighbouring females. Such a mating system means that birds will avoid small forests with few or no other pairs where there are few or no opportunities for extrapair copulations. Birds are very faithful to territories they used in previous years as long as they are still surviving. Birds generally depart summer areas in late August to late September, flying at night, many across the Gulf of Mexico, to reach wintering areas.
Limiting factors
The primary factor limiting Hooded Warblers in Canada is the lack of extensive mature tracts of relatively undisturbed forests. Birds will simply not use small forest patches that cannot provide territories more than 200 m from forest edges for several pairs of birds. If they were to try to nest closer to forest edges, rates of predation and parasitism would likely to be too high. The breeding habitats that it occupies are also home to other relatively rare species such as Acadian Flycatchers, Cerulean Warblers, Louisiana Waterthrushes, and Prothonotary Warblers. Most of the forests they occupy are managed for timber production that is often incompatible to long term use of the forest by Hooded Warblers and other species. Housing developments, recreational vehicles, and invasion by alien plants may also be contributing to degradation of existing habitats. Losses of wintering habitat may also be affecting populations to some extent, but the effect is unknown, and since the species is doing well elsewhere, may not be significant.
Protection
The birds and their nests are protected by the Migratory Birds Convention. Municipal tree cutting by-laws should offer some protection to habitats, but unfortunately are often too loosely enforced or interpreted to offer any substantial protection.
The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) determines the national status of wild species, subspecies, varieties, and nationally significant populations that are considered to be at risk in Canada. Designations are made on all native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fish, lepidopterans, molluscs, vascular plants, lichens, and mosses.
COSEWIC comprises representatives from each provincial and territorial government wildlife agency, four federal agencies (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biosystematic Partnership), three nonjurisdictional members and the co-chairs of the species specialist groups. The committee meets to consider status reports on candidate species.
Species: Any indigenous species, subspecies, variety, or geographically defined population of wild fauna and flora.
Extinct (X) : A species that no longer exists.
Extirpated (XT) : A species no longer existing in the wild in Canada, but occurring elsewhere.
Endangered (E) : A species facing imminent extirpation or extinction.
Threatened (T) : A species likely to become endangered if limiting factors are not reversed.
Special Concern (SC)* : A species of special concern because of characteristics that make it particularly sensitive to human activities or natural events.
Not at Risk (NAR)* : A species that has been evaluated and found to be not at risk.
Data Deficient (DD)*** : A species for which there is insufficient scientific information to support status designation.
* : Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
** : Formerly described as “Not In Any Category”, or “No Designation Required.”
*** : Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994.
The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list.
Environment Canada Environnement Canada
Canadian Wildlife Service Service canadien de la faune
The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.
Introduction
The Hooded Warbler is a small songbird belonging to the large wood warbler (Parulidae) family that is found only in the western hemisphere. It breeds mainly in the eastern United States, and its range extends into Canada only in southwestern Ontario (Fig. 1). They are migrants, moving to Central America, from central Mexico to Panama along the Caribbean side, and several Caribbean islands, for the winter. It was first considered by COSEWIC in 1993 (Page and Cadman 1993).
It was fairly common in the United States where there seemed to have been an overall slight increase in numbers since 1966, according to breeding bird survey results. However, in the adjacent northern states, it was much less common, and had apparently declined considerably in adjacent Michigan (Brewer et al. 1991) if not elsewhere.
As a species requiring extensive patches of mature forest, it was probably a much more widespread breeder in Ontario prior to forest clearing in the 1800’s, but its habitat had become severely depleted. Surveys in the 1980’s and into the early 1990’s had suggested that the population had dwindled to fewer than 200 pairs. Most birds were found in only two areas of Haldimand-Norfolk and Elgin Counties (Fig. 2), and even here the amount of suitable habitat was not large, was fragmented, and there were continuing threats to the remaining habitat (Page and Cadman 1993).
It was clear that the population was very small, but there was some indication that the population had stabilized in recent years. As a result of the above concerns the species was designated Threatened by COSEWIC in 1993.
Population Sizes and Trends
Overall in North America the Hooded Warbler is fairly widespread in the eastern United States, and not in any apparent difficulty. It is rated G5 by the Nature Conservancy. In the longer term there was a significant increase in numbers from 1966 to 1993 according to breeding bird surveys (Price et al. 1995). That trend has continued in recent years with a non-significant increase from 1984 to 1993 (Price et al. 1995) and in 1996 to 1998 (www.mbr-pwrc.usgs.gov/bbs/trend/trend98.html).
In the adjacent U.S. states the species is doing well in many areas. In New York it is rated S5 by the Nature Conservancy (demonstrably widespread, abundant and secure), and considered locally common, mainly in the western half of the state (Andrle and Carroll 1988). It increased significantly between 1980 and 1998 on breeding bird surveys on 15 routes were it was recorded. In Pennsylvania it is ranked S4 (somewhat uncommon, but widespread). It was found somewhat unevenly in breeding bird atlas surveys, but there had been a steady upward trend in numbers from 1968 to 1989 (Brauning 1992). Breeding bird surveys show significant increases from 1966 to 1998 on 60 routes. It is rated S5 in Ohio, is widely distributed, mainly in the eastern half of the state, and is considered to be still expanding its range (Peterjohn and Rice 1991). Breeding bird surveys show moderate non-significant but steady increases from 1966 to 1998 with counts on 30 routes or more. In these three states it has been considered to be increasing in numbers and range through the 20th century, probably as formerly cleared forests have been allowed to regenerate.
In Michigan, however, the situation is more similar to the Ontario experience. It was formerly considered common in forested areas in the southern half of the lower peninsula, but now is very thinly scattered in relatively few areas retaining some forest cover (Brewer et al. 1991). As it was recorded on only 85 atlas squares, it was placed on the list of special concern in the state in 1990. The Nature Conservancy rates it only S2 in Michigan (imperiled). Breeding bird survey data from only 4 routes do indicate, however, that there has been some increase in both the shorter (1980-1989) and longer (1966-1989) term. It is also rated only S2 in Wisconsin and S3 in Illinois, other states near the northern part of its range where forest clearing has been widespread as it has been in Ontario.
In Ontario, at the present time, the Hooded Warbler breeds almost entirely in the Carolinian Forest region near Lake Erie (Fig. 2). However, scattered breeding records north to Georgian Bay, and recent summering in the Kingston region, suggest that at one time it may have been much more widespread when forest cover dominated the southwestern portions of the province. The original forest cover was nearly continuous, with numerous small gaps (Lorimer 1989) well suited for this species. It may have virtually disappeared from the province, however, with forest clearing here and to the south of the province in the adjacent northern states in the 1800s. The bird was scarcely known in the late 19th and early 20th centuries in the province, and nesting was not confirmed until 1940 (Brooman 1954).
Since about 1950, there appears to have been a slow increase in numbers in Ontario. However, it is not clear whether this has been a real increase, or an increase in effort and ability to find the species in remaining habitats. Impressions of regional coordinators for the first breeding bird atlas were that there had been a slight increase (Page and Cadman 1993).
The first estimates of numbers from the breeding bird atlas (1981-1985) suggested an annual population of only about 25-53 pairs. But, because not all habitat was surveyed, the actual population was suggested to have been closer to 100 pairs (Sutherland and Gartshore 1987). There are too few to have been reported on any breeding bird survey routes in Ontario.
A more thorough assessment a few years later, pulling together all available information, estimated a population between 80 and 176 pairs (Gartshore 1988). It was still not clear if there had been an actual increase, however, and numbers were relatively small at best. A further complication in getting numbers, is that they move from place to place as forest conditions change. For example, one of the largest populations was in the South Walsingham forest, but they have declined by more than half in the last few years. However, they have moved into the St. Williams forests where they were not previously found (Whittam 1999).
Surveys of 51 known breeding sites were undertaken in the summer of 1997, in six counties in southwestern Ontario. It was encouraging that they were found at more sites than in previous years, making it clear that they had colonized a few new sites in the past decade. However, they were still found in only 17 sites. The total number found was 88 pairs, and an estimated population for all of Ontario was suggested to be in the order of 145 to 300 pairs (Heagy 1997).
Surveys in 1998, suggested a population of 144 to 207 pairs, with expansion in some places, but localized declines elsewhere (McCracken 1999). These estimates in 1997 and 1998 suggest a population nearly double that of a decade earlier (Whittam 1999). No extensive surveys were undertaken in 1999, but the trend continues to be encouraging, with numbers up in places that were visited (J. McCracken, Pers. Comm.). However, numbers are still small, and until similar surveys are repeated over a period of time, it is not possible to say for sure that this has been a real increase, or that current levels will hold. Hooded Warblers are currently rated S3 in Ontario by the Nature Conservancy.
Habitat
Hooded Warblers nest in mature hardwood forests with tall trees and relatively well closed canopy. Here they occupy small clearings, such as created by a fallen tree, where low dense shrubby vegetation has sprung up. They begin to use an area from one to five years after a clearing has been created naturally or by selective tree removal. They will use the shrubbery for 10 to 12 years, until it exceeds a height of 5 m and begins to shade the ground (Gartshore 1988).
Single tree harvesting, and selective logging in less mature forests, may be used to enhance populations (Annand and Thompson 1997, Gartshore 1988). However, logging, unless done every few years, does not sustain a population in the long term. Natural gaps occur randomly and sustain Hooded Warblers in large tracts (McCracken 1999).
The Hooded Warbler is also considered an area-sensitive species, requiring large tracts of forest. In Maryland the minimum forest area required to sustain a population was 30 ha (Robbins 1979). In Ohio, woodlots occupied were at least 18-22 ha (Peterjohn and Rice 1991). They are inhabitants of forest interiors. Narrow riparian corridors are avoided even though the habitat appears suitable (Peterjohn and Rice 1991). In highly fragmented forests they may suffer extremely high predation rates of up to 80% (Robinson et al. 1995), and high nest parasitism rates that may reach 75% (Annand and Thompson 1999, Robinson 1990, Robinson et al. 1995, Stutchbury 1997, Terborgh 1992). Without large blocks of forest, with much of the area farther than 200 m from the edge, this species is unlikely to persist in the long term.
In presettlement southern Ontario, there were extensive amounts of habitat that would have been suitable for Hooded Warblers – large areas of mature hardwood forest covering most of area south of the Canadian Shield (Lorimer 1989). However, at present, in this area, most counties now have less than 20% forest cover, and in the Carolinian Forest region near lake Erie, most counties have far less than that. The most suitable areas are in Elgin and Haldimand-Norfolk counties where 15-17% forest cover still remains (Riley and Mohr 1994, Riley 1999). In 1891, forest cover in the Carolinian Forest region was only about 19%, and by 1981 it had fallen to only 6.6% (Page and Cadman 1993).
In addition to an overall loss of forest in southern Ontario, much of what remains is highly fragmented. In one of the most heavily forested Carolinian areas, Haldimand-Norfolk Regional Municipality, 99% of forests are smaller than 100 ha and forest-interior habitat, more than 200 m from woodland edges, comprises only 0.39% of forest cover (Pearce 1992, Hounsell 1999). In the whole of the Carolinian Forest region, forest interior covers only about 2% of land area (Cadman 1999). Such fragmentation is the most serious threat to biological diversity, and the primary cause of local and more widespread extinctions (Wilcox and Murphy 1985).
Although some areas of the eastern deciduous forests of North America have shown increased forest cover with farm abandonment and tree planting, this has not been the case in much of southwestern Ontario. Here forest losses continue in many counties (Pearce 1993, Riley 1999). Where there has been some increase, it has mostly been in pine plantations, or other types of plantation that are not well suited to this species.
Remaining Hooded Warbler habitat lies in the most intensively farmed area of Ontario, and agriculture continues to gnaw away at forest cover in many places (Riley and Mohr 1994, Riley 1999). Urban and residential development have continued to expand, each contributing to negative affects on remaining forests through enhancement of predator populations (Friesen et al. 1995), Most forests are subject to logging of some sort, and unless done with concern for forest interior species in mind, it is likely to be detrimental to Hooded Warblers (Robinson et al 1995, Annand and Thompson 1997, McCracken 1999).
There is a provincial woodland protection policy in Ontario, but apparently few municipalities have conformed to the policy. Nor have they bothered to enact tree-cutting bylaws under the Municipal Act. Nor has the Managed Forest Tax Incentive Program encouraged very many to adopt sustainable selective logging practices that might benefit species like Hooded Warbler (Riley 1999). The habitat situation for Hooded Warblers has not apparently improved, and may have worsened.
Evaluation and Proposed Status
Widespread and much more continuous forest cover in southern Ontario prior to European settlement suggests that Hooded Warbler populations could have been much larger at one time. Forest interior and area sensitive species such as Hooded Warblers have suffered the greatest losses with forest clearing (Cadman 1999). Unfortunately we do not know just how extensive they were. Widespread deforestation within the present range of the species in eastern North America, no doubt caused a considerable decline. In recent years the trend in the northern U.S. states south of the Ontario breeding range has been upward, partly due to regeneration of forest cover there (Andrle and Carroll 1988, Brauning 1992, Peterjohn and Rice 1991).
However, in Michigan, at the same latitude, it remains a species of special concern, as its numbers also appear to have declined considerably from former times (Brewer et al. 1991). In the Canadian breeding range, confined to southern Ontario, there appears to have been some increase since 1950, but much of that is only the result of more intensive searching and an enhanced ability to locate and identify the species.
The first estimates of numbers from the 1981-1985 period suggested a population of only 25-50 pairs, but because not all habitat was surveyed, it was expected to have been closer to 100 pairs (Sutherland and Gartshore 1987). Additional and more complete surveys in 1997 and 1998 indicate that 150-200 pairs are likely at the present time (Hagey 1977, McCracken 1999). While apparently encouraging, these numbers are still small, and until similar surveys are repeated, they need to be considered cautiously. There may have been little actual increase, or fluctuations in numbers could reduce counts again.
Hooded Warblers are area-sensitive, forest-interior inhabitants of mature deciduous woodlands. The quantity and quality of forest of forested lands within the range of the species is currently very small (Pearce 1993), most is concentrated in a few areas of Elgin County and Haldimand-Norfork Regional Municipality. Forested lands in the Carolinian Forest region are still subject to losses associated with agriculture, residential development, and unsuitable logging practices (Friesen et al 1999, Riley 1999).
Until we have better data to indicate real population growth, and better controls on removal or disturbance to forested areas, and in view of the overall small population size and continuing threats to habitats, it is appropriate to maintain the Threatened status.
Acknowledgements
Thanks to Colleen Hyslop for the opportunity to prepare this report, and for arranging funding through the Canadian Wildlife Service, Environment Canada. Don Sutherland provided data from the Natural Heritage Information Centre, and personal comments. Jon McCracken forwarded information about recent numbers. Thanks to both of them. Helpful comments were received from Michel Gosselin and David Christie.
Literature Cited
Andrle, R.F. and J.R. Carroll. 1988. The atlas of breeding birds in New York State. Cornell Univ. Press, Ithaca.
Annand, E.M. and F.R. Thompson. 1997. Forest bird response to regeneration practices in central hardwood forests. J. Wildl. Manage. 61:159-171.
Austen, M.J.W., M.D. Cadman, and R.D. James. 1994. Ontario birds at risk. Fed. Ont. Nat, Don Mills.
Brauning, D.W. 1992. Atlas of breeding birds in Pennsylvania. Univ. Pittsburgh Press, Pittsburgh.
Brewer, R., G.A. McPeek, and R.A. Adams. 1991. The atlas of breeding birds of Michigan. Mich. State Univ. Press, East Lansing.
Brooman, R.C. 1954. The birds of Elgin County. Gilbert Press, St. Thomas.
Cadman, M.D. 1999. Conserving what’s left of southern Ontario’s forest birds. In Southern Ontario Woodlands. The conservation challenge. Fed. Ont. Nat., Don Mills. Pp. 24-28.
Evans Ogden, L.J. and B.J. Stutchbury. 1994. Hooded Warbler (Wilsonia citrina). In The Birds of North America, No. 110 (A. Poole and F. Gill, eds.). The Acad. Nat. Sci., Philadelphia, PA, and The Amer. Ornithol. Union, Wash., D.C.
Friesen, L.E., P.F.J. Eagles, and R.J. Mackay. 1995. Effects of residential development on forest dwelling neotropical migrant songbirds. Conserv. Biol. 9:1408-1414.
Friesen, L., M. Cadman, P. Carson, K. Elliott, M. Gartshore, D. Martin, J. McCracken, P. Prevett, B. Stutchbury, D. Sutherland, and A. Woodliffe. 1999. National Recovery Plan for Acadian Flycatcher and Hooded Warbler. RENEW, Ottawa.
Gartshore, M.E. 1988. A summary of the breeding status of Hooded Warblers in Ontario. Ont. Birds 6:84-99.
Heagy, A. 1997. Jury still out on Acadians/Hoodies. Long Point Bird Observatory Newsletter 29(3):14.
Hounsell, S.W. 1999. Southern Ontario 2099. Planning with the end in sight. In Southern Ontario Woodlands. The Conservation Challenge. Fed. Ont. Nat., Don Mills. Pp. 74-91.
Lorimer, C.G. 1989. Relative effects of small and large disturbances on temperate hardwood forest structure. Ecology 70:565-567.
McCracken, J. 1999. Acadians and Hoodies in Ontario. Long Point Bird Obs. and Ont. Projects Newsletter 31:12.
McCracken, J. 1999. Management of forest interior birds in relation to basal area. In Southern Ontario Woodlands. The conservation challenge. Fed. Ont. Nat., Don Mills. Pp. 65-66.
Page, A.M. and M.J. Cadman. 1993. Status report on the Hooded Warbler Wilsonia citrina in Canada. COSEWIC, Ottawa.
Pearce, C.M. 1992. Pattern analysis of forest cover in southwestern Ontario. East Lakes Geographer. 27:65-76.
Pearce, C.M. 1993. Coping with forest fragmentation in southwestern Ontario. In Size and integrity standards for natural heritage areas in Ontario (S.F. Poser, W.J. Crins, and T.J. Beechy, eds.). Prov. Parks and Nat. Heritage Policy Br., Ont. Min. Nat. Res, Toronto. Pp. 100-113.
Peterjohn B.G. and D.L. Rice. 1991. The Ohio breeding bird atlas. Ohio Dept. Nat. Res., Columbus, OH.
Price, J., S. Droege, and A. Price. 1995. The summer atlas of North American birds. Academic Press, CA.
Riley, J.L. 1999. Southern Ontario woodlands: the conservation challenge. In Southern Ontario Woodlands. The conservation challenge. Fed. Ont. Nat., Don Mills. Pp. 9-22.
Riley, J.L. and P. Mohr. 1994. The natural heritage of southern Ontario’s settled landscapes. Ont. Min. Nat. Res., Southern Reg., Sci. and Tech. Transfer, Tech. Rept. TR-001, Aurora, Ont.
Robbins, C.S. 1979. Effects of forest fragmentation on bird populations. In Management of northcentral and northeastern forests for nongame birds (R.M. DeGraff and K.E. Evans, eds.). U.S. Dept. Agric., Tech. Rept. NC-51:198-212.
Robinson, S.K. 1990. Effects of forest fragmentation on nesting songbirds. Illinois Nat. Hist. Survey Report No. 296.
Robinson, S.K., F.R. Thompson III, T.M. Donovan, D.R. Whitehead, and J. Faaborg. 1995. Regional forest fragmentation and the nesting success of migratory birds. Science 267:1987-1990.
Stutchbury, B.J.M. 1997. Effects of female cowbird removal on reproductive success of Hooded Warblers. Wilson Bull. 109:74-81.
Sutherland, D.A. and M.E. Gartshore. 1987. Hooded Warbler. In Atlas of the breeding birds of Ontario (M.D. Cadman, P.F.J. Eagles, and F.M. Helleiner, eds.). Univ. Waterloo Press, Waterloo, ON. Pp. 418-419.
Terborgh, J. 1992. Why American songbirds are vanishing. Sci. Amer. 266(5):98-104.
Whittam, B. 1999. Life beneath the hood; a glimpse into the home life of the Hooded Warbler. Long Point Bird Observ. and Ont. Progr. Newsletter 31(3):9.
Wilcox, B.A. and D.D. Murphy. 1985. Conservation strategy: the effects of fragmentation on extinction. Amer. Nat. 128:879-887.
The Author
Ross James is a Departmental Associate and former Curator of Ornithology at the Royal Ontario Museum in Toronto, Ontario. He studied the foraging behaviour of vireos in southern Ontario, and the ecological and behavioural relationships of Blue-headed and Yellow-throated Vireos for masters and doctoral research at the University of Toronto. He has also conducted bird population studies in boreal forest and southern woodlands and wetlands. He is interested in the status and distribution of birds in Ontario, authoring an Annotated checklist of Ontario Birds, and coauthoring two volumes on the Breeding Birds of Ontario. He was a committee member for and a contributor to the Atlas of Breeding Birds of Ontario, and a coauthor of Ontario Birds at Risk. He is an author of two accounts for the Birds of North America, and has published more than 80 papers on birds. He spent more than a decade as chair and cochair of the Birds Subcommittee of COSEWIC. In this capacity he was familiar with previous status reports and the status of this species.
Knowledgeable Persons
M.E. Gartshore, R.R. #1, Walsingham, ON. NOE 1X0.
J. McCracken, Bird Studies Canada, P.O. Box 160, Port Rowan, ON. NOE 1M0.
D.A. Sutherland, Natural Heritage Information Centre, 300 Water Street, P.O. Box 7000, Peterborough, ON. K9J 8M5.
B.J. Stutchbury, Dept. Biol, York University, North York, ON.
Woodliffe, Ont. Min. Nat. Res., P.O. Box 1168, Chatham, ON. N7M 5L8.
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