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The Status andDistribution of the

Prairie Warblerin Ontario

byAnne B. Lambert and Roy B.H. Smith

The Prairie Warbler (Dendroicadiscolor) has been considered arelatively rare breeding species inOntario, but one whose exactstatus was rather poorly known.This led the Nongame Program ofthe Ontario Ministry of NaturalResources to commission a studyof its status in Canada, and earlyin 1984 a report was prepared(Lambert and Smith 1984). TheStatus Report detailed informationavailable up to 1983, based on theliterature and communicationswith knowledgeable birders, whilethis paper summarizes those data.Additional information obtainedduring the 1984 season has alsobeen included, when available.

OverviewIn Canada, the Prairie Warblerhas been reported in five provincesbut has been proved to breed onlyin Ontario. It is a very rare springmigrant in Quebec (7 or 8records), and a rare but regular fallmigrant in New Brunswick andNova Scotia (mainly on offshore

islands), where over one hundredhave been recorded. There are alsothree fall records from Newfoundland

In Ontario, the Prairie Warblerwas first recorded in 1900 (Samuel1900; Ames 1901) and was firstproved to breed in the province in1922 (Harrington 1922). Histor­ically, breeding has beenconfirmed in ten Counties/Districts (Lambton, Haldimand­Norfolk, Waterloo, Dufferin,Bruce, Simcoe, Muskoka, ParrySound, Peterborough, Frontenac)and suspected in six more(Middlesex, Manitoulin, Hastings,Prince Edward, Leeds andGrenville, Lanark). Presently,however, breeding occurs on aregular basis in only six Countiesor Districts (Lambton, Simcoe,Muskoka, Parry Sound, Peterbor­ough, and Frontenac). The mainstronghold of the Ontariopopulation is concentrated alongthe eastern shore of Georgian Bayin the Districts of Muskoka andParry Sound, with smallernumbers in Frontenac and

Anne B. Lambert and Roy B.H. Smith, Box 222, Port Rowan, OntarioNOE IMO

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: Georgian Bay breeding range

• other regular breeding sites (current)

• isolated breeding record

• possible breeding siteso former breeding sites

Figure 1. Breeding distribution of the Prairie Warbler in Ontario:1900-1984.

Peterborough (Fig. 1). In theseareas the population appears to bestable f although a slight increasemay have occurred in Frontenac.However, in Simcoe and LambtonCounties substantial declines havebeen documented.

Breeding HabitatsAt least three distinct habitat typeshave been occupied in Ontario, allcharacterized by open, scrubbyvegetation and usually zericconditions. The most importanthabitat is the pine-oak-juniperscrub found along the GeorgianBay shoreline and at scatteredlocations along the southern edgeof the Canadian Shield (e.g. inPeterborough and FrontenacCounties). This open,- rockyhabitat (often only 50% vegetated)

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is typically dominated by maturebut stunted white pine (Pinusstrobus), white and red oak(Quercus alba, Q. rubra), and bypatches of common juniper(Juniperus communis var. depres­sa). Prairie Warblers mostfrequently select these low junipersfor nest sites (Lord 1955; D.A.Sutherland, pers. comm.). Recent­ly, use of a similar habitat alongsome hydro line rights-of-way inFrontenac Co. has also beenreported (RD. Weir, pers.comm.).

The second important Ontario~abitat is a sand dune habitatexemplified by the Lake Hurondunes at Pinery Provo Park(Lambton Co.) and, formerly, atWasaga Beach (Simcoe Co.), oncethe site of a large'colony'. At the

Pinery, the 'interdunal meadows'frequented by Prairie Warblerscomprise a fairly open habitat with"scattered mature black oak; lowshrubs ofjuniper, fragrant sumac,wild grape, choke cherry and redcedar~alllow, vegetation withclumping evident" (T. Crabe, pers.comm.). A detailed description ofthis habitat has been provided bySparling (1965).

In the Turkey Point/St.Williams area (Haldimand-NorfolkRM.), sandy plains with plantedpines and!or deciduous scrubcomprise a third habitat type.This open, successional habitattypically includes pin cherry(Prunus pensylvanica), saplingoaks (Quercus spp.) and otherdeciduous species. The plantationsonly remain suitable as nestinghabitat for 10 to 20 years (A.Wormington, pers. comm.), butsequential plantings by theProvincial Forestry Station haveprovided a virtually continuoussupply of habitat since the early1930s. Second growth deciduousscrub is used much morefrequently within the PrairieWarbler's United States range, theonly other Ontario examples beinga single case of breeding inWaterloo RM. in 1982 and one ofpossible breeding in MiddlesexCo. in 1983. An instance ofpossible breeding has also beenrecorded in old fields regeneratingto red cedar (Juniperus vir­giniana) in Prince Edward Co. in1979.

Detailed Bre~dingDistribution

Lambton County. Prairie Warblers

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were first recorded at Port Franksin 1915, and during the 1930s atleast 26 singing males were notedover an 8 km length of dunes(Saunders 1934, in litt.). At thisdensity there could have been 50pairs or more in the entire area ofhabitat between Ipperwash andGrand Bend. Indeed, after theRoyal Ontario Museum's collect­ing trip to the area in 1935, Snyderwas said to have described thePrairie Warblers there as"positively abundant" (J.L. Baillienotes, ex ROM files). However,cottage development has probablycontributed to a decline in thepopulation since the 1930s, andwithin Pinery Provo Park theplanting of pines on somesecondary and tertiaiy dunesduring the 1950s may have led tosome reduction in habitat (J.D.McCauley, pers. comm.). In recentyears, increasing visitor pressurescould also have had some effect(T. Crabe, pers. comm.).

In 1969 the population wasestimated at 17-22 males (J.LameY,fide T. Crabe, pers.comm.), but since then thereappears to have been a slowdecline. Figures for someintervening years are not available,but from 1977 onwards thenumbers of singing males wereestimated as follows: 1977 - 10 to20; 1978 - 11 +; 1979 - 7?; 1980­between 4 and 8, probably 6; 1981- between 6 and 8, probably 8;1982 - 5+; and 1983 - 5 (T.Crabe, pers. comm.; J.D.McCauley, pers. comm.). Thepresent Pinery population seems tobe stable at between 5 and 8singing males, and the total

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population for the entire areabetween Grand Bend and KettlePoint has been estimated at 10pairs (T. Crabe, pers. comm.).

Middlesex County. The PrairieWarbler has never been proved tobreed in Middlesex, but twosummer records in the Londonarea in 1930 and 1931 raised thepossibility that breeding mighthave occurred (Saunders and Dale1933). More recently, a singingmale was observed in the' Skunk'sMisery' area, Mosa Twp. on 1, 4and 14 July 1983, again suggestingthe possibility of breeding. Thisbird was occupying a successionalhabitat described as a mixture oflow pines, birch and aspen,interspersed with clearings (S.Connop, pers. comm.).

Haldimand-Norfolk RegionalMunicipality. Published andunpublished records indicate thatin the early 1930s a small breedingpopulation was discovered in theTurkey Point-St. Williams area, inpine plantations established by theSt. Williams Forestry Station. In1936 a 'colony' of six males wasreported at Turkey Point by G. W.North (Toronto OrnithologicalClub records,per ROM files) andbreeding was confirmed on 15 July1942, when a nest with threeyoung was found in SouthWalsingham (now Norfolk) Twp.(F. North 1943, in. litt.). A smallpopulation persisted in the St.Williams Forestry Station throughthe next few decades as phasedplantings kept a supply of suitablehabitat available for about 50years, but by 1971 it was noted

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that suitable habitat wasdisappearing (Goodwin andRosche 1971). Although completecounts or censuses were notconducted, the numbers involvedwere probably quite small. Thehighest recorded count of eightsinging males was made in 1972(A. Wormington, pers. comm.),and the slow decline since thattime can be attributed to theincreasing maturity of the pineplantations. The last year in whichsinging males (2 or 3) wererecorded was 1979 (R.J. Curry,pers. comm.; C.J. Risley, pers.comm.), but in 1984 a pair and anadditional singing male werelocated by the authors at a sitenear Turkey Point. Althoughbreeding was not confirmed, thisfind suggests that the PrairieWarbler may yet persist as abreeding species in Haldimand­Norfolk R.M.

Waterloo Regional Municipality.There is a single, unprecedentedbreeding record from 1982, when anest with eggs was found nearBamberg, Wilmot Twp. by R.Pickering (P.F.J. Eagles, pers.comm.). The habitat was describedas "second growth forest withnesting Golden-winged Warblersas well".

Dufferin County. The singlerecord concerns a nest with 5 eggsfound on 11 June 1927 onShrigley Creek, Melancthon Twp.by Dr. P. Harrington (OntarioNest Record Scheme - hereafterONRS). The nest was located injuniper, but it is not known

whether appropriate habitat existsin this area today.

Bruce County. Observations ofsinging males suggest that breedingmay have occurred at the followinglocations: near Cameron Lake, St.Edmunds Twp. in 1905 (Saunders1906); at Colpoy's Bay,Albemarle Twp. in 1908 and 1909(Klugh 1909,1910); at McVicar,St. Edmunds Twp. in 1928, 1930and 1934, at Stokes Bay, EastnorTwp. in 1928, and at Oliphant,Amabel Twp. in 1933 (J.L. Baillienotes, ex ROM files). Collectively,these records suggest that smallbreeding populations may havebeen present along the BrucePeninsula; but it was not until1953 that breeding was confIrmed.Previously unpublished informa­tion supplied by B. Krug (pers.

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comm.) indicates that he located a'colony' of about 8 pairs in St.Edmunds Twp. in 1952. In 1953he found a nest with young, butthere were fewer breeding pairs,and in the following years thecolony continued to decline, fInallydisappearing after 1958.

More recently, the late GeorgeNorth is reported to have seenPrairie Warblers at Miller LakeLindsay Twp. in the 1950s and'1960s (J. Miles, pers. comm.),while occasional sightings ofsinging males have occurred duringthe years 1975 to 1982 (near CapeHurd, St. Edmunds Twp.; ChiefsPoint Indian Reserve; and RedBay, Amabel Twp.). Although1981-1983 Ontario Breeding BirdAtlas fIeldwork has failed toprovide any records (M. Parker,pers. comm.), areas of ap­parently suitable habitat stillexist, particularly along thewestern side of the peninsula (T.Cheskey, pers. comm.; D.A.Sutherland, pers. comm.). Hencethe possibility remains that theoccasional pair may yet be foundbreeding on the Bruce Peninsula.

Manitoulin District. ConfIrmedbree?ing records are lacking, buttwo Instances of singing males inJune and July have indicated thepossibility of breeding. In 1970two singing males were present 'inBu~e~ Twp., 29 June to 16 July,whIle In 1974 three singing maleswere noted in suitable habitat atBelanger Bay (Dawson Twp.) on22 May. However, these birds hadmoved away by the following week(Goodwin and Rosche 1974'Nicholson 1981). In additio~ tothese records on Manitoulin

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Island, there are three springrecords (2 in 1978; 1 in 1979) ofsingle males elsewhere in theDistrict. However, these probablyrepresent'overshooting' springmigrants, and none have beenreported during 1981-1983 Atlasfieldwork (D. Ferguson, pers.comm.).

Simcoe County. In 1915 a large'colony' of Prairie Warblers wasfound amongst the sand dunes withscattered oaks, pines and juniperbordering Nottawasaga Bay(Wasaga Beach). "Upwards of200 birds" were seen by Dr. P.Harrington (J.L. Baillie notes, exROM files), while in 1919 it wasestimated that 150 pairs wereoccupying the three miles fromOakview to the mouth of theNottawasaga River (Devitt 1967).In 1921, it was found that thebirds "were localized and followedthe shoreline for about 15 miles,never further than 200 yardsinland" (Harrington 1922), hencethere could have been considerablymore than 150 pairs. Whatever its

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exact size, this population musthave represented the largest andmost concentrated group ofbreeding Prairie Warblers everknown in Ontario.

On 19 June 1922, the firstPrairie Warbler nest for Canada(containing 2 young and a youngcowbird) and three additional nestswere found at Wasaga Beach by P.Harrington and F.A.E. Starr(Harrington 1922). However,following World War I, the colonydeclined rapidly as "the extensivebuilding of summer cottages alongthis beach encroached upon itsbreeding territory" (Devitt 1967).By 1-933 only a small populationremained in the vicinity ofAllenwood Beach and by the early1940s this too had disappeared. In1948 Devitt found a remnantpopulation of at least five singingmales at the nearby BluewaterBeach, but in a subsequent surveyon 23 June 1967, Devitt failed tofind any Prairie Warblers.

Two other breeding sites areknown in Simcoe Co. One is alongthe rocky banks of the Severn

River in Matchedash Twp., wherein June 1938 "many singing maleswere observed from Hydro Glen,near the entrance of Sparrow Lakedown to Tea Lake", a distance of14 km (Devitt 1967). The other isat Burrows Bay on GloucesterPool, where Mr. and Mrs. A.G.McVicar (pers. comm.) haveobserved two or three pairs ofPrairie Warblers annually for thelast 10 or 15 years, and havefound several nests.

Another possible breeding site islocated 2 km west of LakeCouchiching in OriIlia Twp.,where W.E. Cattley (pers. comm.)has found singing male PrairieWarblers during the breedingseason. The site is a small area oflimestone outcropping, andcommon juniper is the dominantvegetation.

Muskoka District Municipality.The earliest known locations areGo Home Bay, where animmature male was collected on 1August 1904; Beausoleil Island,where six birds were observed on12 August 1929 (Dingman 1929,in litt.); and Honey Harbour,where two were collected in June1931. P. Saniford (1933, in litt.)wrote of having seen pairs ofPrairie Warblers at Go Home Bay"during the last 20 years", andJ.B. Armstrong confirmed breed­ing there in 1933, 1934 and 1936(D.M. Fraser, pers. comm.).

It was not until 1955, however,that any observations concerningthe Georgian Bay population werepublished (Lord 1955). Later, theGibson River became known asanother possible breeding location,and directions to this site, where

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"up to a dozen" singing maleshave been observed, were given byBrewer (1972). The north shore ofMcCrae Lake was also identifiedas a breeding site (Brewer 1972;Hanna 1979), while Mills (1981)added Go Home Lake to the list ofpublished Muskoka breeding sites.In addition, extensive butunpublished personal data,representing a compilation ofabout 15 years' observations, weremade available by D.A. Sutherlandand D.M. Fraser (pers. comm.).Based on these data (as opposed tospecific counts or censuses), thepresent coastal Muskoka popula­tion was estimated at around 152singing males. The birds seem toprefer sites close to water (often onislands, peninsulas and bays), buteven in these preferred areas,Prairie Warblers are absent fromsome areas of apparently suitablehabitat, and there are often gapsbetween individual territories(D.A. Sutherland, pers. comm.).

In the southern sector ofMuskoka, the range indicated bySutherland and Fraser extendsfrom Honey Harbour and thenorth end of Beausoleil Island,north amongst the islands (e.g.Minnicognashene Island, MaxwellIsland) to Franceville andHangdog Islands, with 51 singingmales being estimated in thissector. In the Go Home Bay area,which extends from High RockIsland north to the TadenacPeninsula and as far east as GoHome Chute, 80 singing maleswere estimated. Another two birdswere noted at O'Donnell Point,but the only known' inland' siteswere at Go Home Lake, McCraeLake, Gibson River and Baxter

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Lake (together accounting foranother 27 singing males).However, additional birds (about 7singing males) were found in 1984at previously unreported sites onTwelve Mile Bay and near MoonRiver in Georgian Bay Twp. (H.Currie, pers. comm.).

In summary, recent estimatesindicate a present population ofabout 167 territorial males inMuskoka D.M. In the Go HomeLake Area, J.B. Falls (pers.comm.) considered that there hadbeen a slow decline since the late1950s/early 1960s, but elsewherethe population appears to be stable(D.A. Suthe~land, pers. comm.).

Parry Sound District. Thesituation in Parry Sound is muchless well known than in Muskoka,but breeding populations extendnorth to at least Franklin Islandand possibly as far as Pointe auBaril. The first record occurred on6 June. 1918, when W.E. Saundersobserved 3 singing males at SnugIsland, northwest of Parry Sound,but most present information onthe species comes from abiological study of the BlackstoneHarbour-Moon Island ProvincialPark Reserve (Simpson andSimpson 1973). This extensivearea is situated southwest of thetown of Parry Sound, inArchipelago Twp., and extendsfrom Woods Bay, Moon River Bayand the south end of Moon Islandnorthwards to include Spider andCowper Lakes. The Simpsonsfound a substantial population ofPrairie Warblers in this region,and identified extensive areas ofpotential habitat.

Other known locations for

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Prairie Warblers include LoonIsland (off Twelve Mile Bay);Ouimet Point and Davey Island inKillbear Provo Park; FranklinIsland; and Oastler Lake (Mills1981); while RL. Bowles (pers.comm.) added Crane Lake and thearea "as far east as Hwy 69around Lake Joseph".

The status in northern ParrySound District, Le. northwest ofthe town of Parry Sound, is stillpoorly known. The most northerlylocation where breeding has beenconfirmed is in 10 km square17NA44, located northwest ofBrooks Landing (M.D. Cadman,pers. comm.), but there is also aJune 1933 record from Frank'sBay on Lake Nipissing (Rickerand Clarke 1939). Hence it ispossible that additional fieldworkcould extend the known range inthis area, perhaps even as far northas the "French River Study Area"(between Killarney Provo Park andLake Nipissing), where Brunton(1979) noted "excellent habitat"and felt that the species "should belooked for". However, duringsummer 1984, brief checks ofseveral areas from Pointe au Barilnorthwards (Bayfield Harbour,Byng Inlet, Key Inlet, FrenchRiver Station and Pickerel River)yielded negative results (D.A.Sutherland, pers. comm.).

As regards numbers, D.A.Sutherland and D.M. Fraser (pers.comm.) estimated 37 singing malesin southern Parry Sound District,south of a line from Wreck Islandto the southern end of MoonIsland. Most were concentratedaround Loon Island and the northside of the entrance to TwelveMile Bay. For the Blackstone

Harbour-Moon Island area,Simpson and Simpson (1973)estimated 200 pairs, but based onthe amount of habitat theyidentified, and extrapolation fromknown Muskoka areas, weobtained revised estimates ofbetween 62 and 162 pairs. Inareas north of Parry Sound wearrived at tentative estimates of 53to 159 pairs, after examining1:50,000 topographic maps.

When the known and estimatedfigures are combined, a provisionalestimate of somewhere between150 and 360 pairs is obtained forthe total Parry Sound population.Additional fieldwork is essential inorder to refine this estimate.

Peterborough County. ThePrairie Warbler does not seem tohave been reported fromPeterborough County prior to1947, when a nest was found atKashabog Lake (Burleigh Twp.,ONRS). Since then, however,breeding sites have been found at

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Long Lake (near Apsley), CoxLake, Coon Lake and StoplogLake (all in Burleigh andAnstruther Twp.); and MethuenLake, Kashabog Lake and RoundLake in Belmont and MethuenTwp. (D. Sadler, pers. comm.).The Long Lake colony is probablythe best known, and was describedas thriving in 1964 (Goodwin1964). On 28 June 1979, G.Carpentier (pers. comm.) counted10 singing males there, while otherestimates range from 5 to 15,"depending upon time of year andday" (RD. McRae, pers. comm.).Specific counts for the other sitesare not available, but we haveestimated a Peterborough po­pulation of at least 20 pairs,perhaps as high as 40-60.

Hastings County. A possiblebreeding site exists at Mt. Moriah,Elzevir and Grimsthorpe Twp.,where a singing male was locatedin June of both 1982 and 1983.These are the only records for

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Hastings Co., where suitablehabitat seems to be very limited(RD. James, pers. comm.).

Prince Edward County. Althoughthere are no confirmed breedingrecords for the County, in July1979 singing males were located attwo sites 15 km west of PrinceEdward Point "Singing occurredthroughut July with 5 males at onesite and at least one male at theother" and the birds occupied aregenerating field "overgrown withsmall red cedar and, at one site,interspersed with aspen" (T.Sprague, pers. comm.). It is notcertain whether these birds werebreeders, non-breeders or failedbreeders (RD. McRae, pers.comm.), and the sites were notoccupied in subsequent years.

Frontenac County. Breeding wasfirst confirmed in 1933 when asmall colony was found at CrossLake, Kennebec Twp., by RV.Lindsay. Another nest was foundthere in 1947 and yet another in1953 (ONRS), but in themeantime other breeding locationsfor Prairie Warbler were beingdiscovered in the southern part ofthe County (Quilliam 1973). In

. northern Frontenac, summeringbirds were noted near Ompah inthe 1950s (H.G. Lumsden, pers.comm.), and a colony wasdiscovered at Mazinaw Lake, BonEcho Provo Park in 1971(Goodwin and Rosche 1971).More recently, 1981-1983 Atlasfieldwork has yielded furtherrecords in the southern part of thecounty including the previouslyunreported finding that hydrorights-of-way were being utilized in

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some areas (RD. Weir, pers.comm.). In the northern part of thecounty, another hydro line site wasfound near Ompah in 1984 (P.Taylor, pers. comm.).

In addition to the sitesmentioned above, known localitiesnow include Devil Lake, CanoeLake (for directions to this site seeGoodwin 1982), Clear Lake, andLake Opinicon (all in BedfordTwp.), while smaller numbers havebeen found in 10 km squares18UE72 (Gould Lake), 18UE44(Puzzle Lake), and 18UE74(Fermoy). In total, Weir (pers.comm.) estimated between 35 and50 breeding pairs of PrairieWarblers in southern FrontenacCo. in 1983. When the northernpart of the county is included, weconsider that the total Frontenacpopulation could amount to 50-65pairs, with the possibility of yetmore being discovered in remoteareas. For example, there may beareas of suitable habitat along theMississippi River (D.A. Suther­land, pers. comm.).

The United Counties of Leedsand Grenville. Just two records ofsinging males suggest thepossibility of breeding. In summer1976 a singing male was presentthroughout May and June at theSlim Bay Peninsula on CharlestonLake, in Charleston Lake ProvoPark (Bell 1977). It was not foundin 1978, but in that year one waslocated at the nearby KillingbeckLake, where the habitat isprobably marginal (D.A. Suther­land, pers. comm.). However,there may be other areas ofpotential habitat in this county andadditional fieldwork could still

yield new discoveries.

Lanark County. The first recordsfor this county were obtainedduring 1984 Atlas fieldwork, when3 or 4 singing males were foundalong railroad tracks north ofChristie Lake (P. Taylor, pers.comm.). The open, rocky, juniper­type habitat was similar to thatused at other Shield edge locations.

Migrant RecordsThroughout southern Ontario, thePrairie Warbler is considered to bea rare or very rare migrant in bothspring and fall. Most records haveoccurred at known concentrationpoints such as Point Pelee,Rondeau and Long Point on LakeErie, or Presqu'ile and PrinceEdward Point on eastern LakeOntario. The heavily populatedareas of Hamilton, Toronto andDurham RM. have also yielded anumber of records. Among thesesites Point Pelee is pre-eminentfor s~ring migrants, and at all sitesexcept Long Point and DurhamRM., spring records greatlyoutnumber those in fall. This isprobably because in spring, birdsare easier to locate and there ismore birding activity. In fact, LongPoint data indicate that similarnumbers are recorded in bothseasons (averaging 2 per year -inrecent years). Over the last 20years, the Long Point BirdObservatory has trapped 2.7Prairie Warblers for every 10,000warblers (all species) banded,which provides some measure ofthe species' rarity as a migrant.

Most records of migrantsinvolve single individuals, but at

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Point Pelee a maximum count offour was recorded on 9 May 1953.There are also records of three on24 April 1977, 11 May 1979, and15 May 1980 (A. Wormington,pers. comm.).

Normal spring migration datesat Point Pelee fall between 1 and23 May, with record early and latedates of 16 April (1982) and 29May (1979), respectively. Thesedates reflect the pattern throughoutsouthern Ontario, although a fewearly June dates have beenrecorded (latest 6 June 1967 atHamilton, apart from a 16 June1969 date at Presqu'ile ProvoPark). The earliest dates of arrivalon the breeding grounds are 2 May(1965) at Clear Lake, Frontenac,and 5 May (1981) at Beausoleil .Island, Muskoka, but the averagedate of arrival on the Frontenacbreeding grounds (based on 13years' data) is 12 May (Quilliam1973).

F all dates at Point Pelee rangefrom 10 August to 20 September,while elsewhere in Ontario theearliest fall date seems to be 7August 1977, at Long Point.Probably, most have departed byearly September (A. Wormington,pers. comm.). The latestdocumented date is 12 October1975 at Mississagi Light,Manitoulin (Nicholson 1981), butonly four October records havebeen located. Full detailsconcerning these and other migrantrecords have been provided in theStatus Report (Lambert and Smith1984).

DiscussionAs outlined in the precedingsections, present day breeding

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populations of Prairie Warblers inOntario are concentrated in areasof Muskoka and Parry Soundfringing Georgian Bay, and inPeterborough and FrontenacCounties. Together, these areasaccount for over 90 per cent of thepopulation. In total, there was in1984 a known Ontario populationof between 321 and 336 pairs (seeTable 1), but the figure couldamount to between 450 and 700approximately, if allowance ismade for those possibly present inpoorly known areas (e. g. northern

Parry Sound District). However,we believe that the lower estimateis more likely: hence in roundfigures the Ontario populationprobably does not exceed 500pairs.

Preliminary data from theOntario Breeding Bird Atlas (Fig.2) indicate that the present (1981­1984) distribution does not differgreatly from the known historicrange (Fig. 1), except, possibly, inBruce Co. To date, PrairieWarblers have been reported inthe breeding season from 38 ten

Table 1: Estimated numbers of Prairie Warblers (pairs or singing males)presently breeding in Ontario (data to 1984).

Known as of Estimated EstimatedCounty/District 1983/84 additional total

Lambton 10 - 10Middlesex - 1 1Haldimand-Norfolk 1 1 2Waterloo - 1 1Bruce - 5 5Simcoe 3 10 13Muskoka 167 8 175Parry Sound 67 85-291 152-358Peterborough 20 20-40. 40-60Hastings - 1 1Prince Edward - - -

Frontenac 50-65 10 60-75Leeds & Grenville - 2 2Lanark 3 1 4Manitoulin - 2 2

Total: 321-336 147-373 468-709

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km squares in Sector 1, withconfirmed breeding in 7 squares,and probable and possiblebreeding in 15 and 16 squares,respectively. However, a concertedeffort during the last year of Atlasfieldwork might relocate thespecies in some former haunts,including the following 10 kmsquares with historic summerrecords but still lacking Atlasrecords: Region 4: 17MT54;Region 5: 17NT42; Region 8:17MA40, 17MA50, 17MA60,17MV69, 17MV85; Region 9:17NU59; Region 13: 17NV96,17PV07, 17PV25; Region 16:17QV14, 17QV15, 17QV24,18TE64; Region 18: 17NA60,17NA80, 17NV98, 17PV16;Region 20: 18UD36; Region 25:18UE45; Region 28: 17NA52,17NA81; Region 33: 17LA47.Birders are encouraged to checkthese areas in 1985.

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For the most part PrairieWarblers in Ontario have utilizednatural rather than man-alteredhabitats. Presumably they havebred for centuries in rocky scrubareas bordering Georgian Bay andthe southern fringe of theCanadian Shield and in the dunalhabitats bordering Lake Huron.Apart from Wasaga Beach and thePinery area, significant threats tothese habitats have not beenidentified; hence the presentsituation is one of relative stabilityand security.

By contrast, man-alteredenvironments have been used to amuch greater extent in the UnitedStates (Nolan 1978), and as aconsequence there has been aconsiderable expansion during thiscentury in the U. S. breeding range(which includes parts of about 31states east of the Great Plains).Recent range expansions have

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SECTOR 1

Figure 2: Breeding distribution of the Prairie Warbler in Ontario, basedon preliminary (1981-1984) data from the Ontario Breeding BirdAtlas. Within 10 km squares: square=confirmed breeding; largecircle=probable breeding; small circle=possible breeding.

been noted in several northernstates, such as Ohio, New York,Vermont, Maine, and possiblyWisconsin; while in Michigan,range expansions in some areashave been offset by contractions inother areas, hence the overallsituation remains dynamic (Walk­inshaw 1959; Payne 1983). Newlyexploited habitats include regen­erating old fields, logged areas,power line rights-of-way, striJrmined areas and young coniferplantations. In Ontario, however,these habitats have rarely beenused, apart from the three casesmentioned previously.

In much of the Ontario range,habitats that appear suitable seemto be under-utilized, and breedingdensities are generally very low

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compared with many parts of theU.S. range. Although data arelacking, we suspect that thisreflects a lower productivity, whichmight result from a shorterbreeding season, a harsherclimate/microclimate, possiblygreater effects of cowbirdparasitism, or other factors.

While the Prairie Warbler'sfuture on its Ontario breedingrange seems secure, the situationin the Caribbean wintering areas ismore difficult to assess. In winter,Prairie Warblers appear to bemost abundant on the Bahamas,fairly numerous on the GreaterAntilles and much less common inthe Lesser Antilles. However,destruction of the various scrubforest habitats used by wintering

birds is an ongoing process,particularly in the GreaterAntilles, and its effects on thePrairie Warbler are largelyunknown.

In conclusion, the PrairieWarbler is not endangered,threatened or rare in many parts ofits range. Nonetheless, the Ontariopopulation is small, localized andperipheral to the main breedingrange, and the Prairie Warblerwarrants designation as a 'rare'species in Ontario (and Canada).

AcknowledgementsWe would like to thank all those115 people who responded to ourquestionnaire, since without theirhelp the Status Report could nothave been written. In particular,Don Sutherland and Don Fraserprovided a wealth of information.Others who contributed Canadiandata were: K.F. Abraham, J.B.Armstrong, M. Bain, D. Barry, M.Biro, C. Blomme, J. Bouvier, RBowles, D. Brewer, G. Carpentier,W.E. Cattley, T. Cheskey, G.F.Clay, C. Cochrane, S. Connop, T.Crabe, D. Cuddy, H. Currie, RCurry, M.P. Davis, O.E. Devitt,B. DiLabio, P. Eagles, G.Fairfield, J.B. Falls, D. Ferguson,D. Fidler, J. Francis, M. Gawn,W.G. Girling, B. Gorman, M.Gosselin, C.G. Harris, W.C.Harris, B. Hartley, D.J. Hawke,'J.M. Immerseel, W.R Jarmain,J.W. Johnson, A.J. Kelley, D.Kerr, R Knapton, S. Kozak, H.Krug, R Lawrence, J.B. Leather,H. Lumsden, J.D. McCauley, J.McCormick, T. McDonald, W.D.McIlveen, S. McKinley, I.McLaren, K. McLaughlin, RD.McRae, A.G. McVicar, J. Miles,

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A. Mills, B. Morin, G. Murphy,D. Myren, J. Nicholson, H.Ouellet, B. Parker, M. Parker, S.Peruniak, J.K. Reynolds, P.Richter, A. Rider, R Ridout, C.J.Risley, P. Ritchie, K. Robinson,D. Rupert, D. Sadler, J.M. Speirs,T. Sprague, P. Taylor, R Tozer,R Tymstra, R Weir, P.A.WoodlifTe, A. Wormington and theLong Point Bird Observatory. Weare grateful to the OntarioBreeding Bird Atlas and itscoordinator, Mike Cadman, formaking available preliminary Atlasresults from 1981-1984, whileRoss James provided access toONRS records and other data heldat the Royal Ontario Museum. Wethank Irene Bowman, MikeCadman and Don Sutherland forhelpful comments on an earlierdraft of this paper. The StatusReport was prepared for theNongame Program of the WildlifeBranch, Ontario Ministry ofNatural Resources, and we thankthe O.M.N.R for permission topublish information contained inthe Report.

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