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The Journal of the Ontario Field OrnithologistsVolume 14 Number 1 April 1996

26

Recognizable FormsCory's Least Bittern

byRon Pittaway and Peter Burke

IntroductionThe secretive Least Bittern(lxobrychus exilis) is the smallestheron in the world, barely biggerthan a meadowlark! In southernOntario, it is a "rare to locallycommon summer resident" fromearly May to mid-September (James1991), mainly south of theCanadian Shield. Least Bitternsin Ontario prefer extensive cattail(Typha) marshes with scatteredareas of open water. They aremost numerous where the ratio ofemergent vegetation cover to openwater is one to one, knownas the 50:50 or "hemi-marsh"stage (Gibbs et al. 1992). Peakactivity periods are dawn and dusk.The male's song (often heard atnight) is a series of five or six lowcuckoo-like notes coo-coo-coo-coo-coo repeated at regularintervals. A cackling ea-ea-ea-ea isheard at all times of the year. Thislatter call could be confused with aKing Rail (Rallus elegans) (JonDunn, pers. comm.).

A very rare colour morph,known as the Cory's Least Bittern,was formerly thought to be adistinct species. In Cory's, the buffsand whites of typical birds are arich chestnut to chocolate. See thecover illustration by Barry KentMacKay and Figures 1 to 3. Cory'sLeast Bitterns are also illustrated inChapman (1896), Pough (1951) and

ONTARIO BIRDS APRIL 1996

Peterson (1980). Cory's LeastBittern is of great interest toOntario birders because more than50 per cent of the records are fromOntario, mainly Toronto. In thisarticle, we review the taxonomy,morph genetics, plumages andmolts, description, fieldidentification, history anddistribution of the Cory's LeastBittern in Ontario.

TaxonomyThe Least Bittern comprises fivefairly similar subspecies (races) inNorth and South America. TheAmerican Ornithologists' UnionCheck-list (AOU 1957) and Palmer(1962) list two subspecies north ofMexico: nominate I. e. exilis in theEast and I. e. hesperis in the West.Recent studies do not support therecognition of hesperis (Gibbs etal. 1992). We follow the latter here.The subspecies found in Ontario isnominate exilis (James 1991).Hancock and Kushlan (1984) givebrief descriptions and ranges of theother four subspecies :erythromelas, peruvianus,bogotensis and pullus.

The type specimen of Cory' sLeast Bittern was taken in 1885near Lake Okeechobee, Florida andwas described as a new species,Ardetta neoxena (Cory 1886). Corydid not give it an English name.Unofficially, it was called Cory's

Bittem by Scott (1892), Mcllwraith(1894) and a few later authors. TheAOU Check-list (AOU 1895)accepted Ardetta neoxena as a fullspecies and officially named itCory's Least Bittem. The AOUnamed it after Charles Bamey Cory(1857-1921), an Americanornithologist best known for theshearwater whose name alsocommemorates him (Terres 1982,Choate 1985).

The scientific name changedseveral times from Ardettaneoxena to Botaurus neoxenus,back to Ardetta neoxena, then toIxobrychus neoxenus, and finally toIxobrychus neoxena (Cory 1886,AOU 1895, Chapman 1896, AOU1931).

Chapman (1896) consideredCory's a distinct species based on10 of the 14 known specimens atthe time. Comparing typical Leastand Cory's, Chapman said, "Thiscomparison shows such a strikingdifference between these two birds,that to give further reasons forregarding them as specificallydistinct seems much like proving anaxiom." Also, O.E. Baynardreported that both nesting adultswere always dark, evidencesupporting Cory's as a distinctspecies (Bent 1926, Bent andCopeland 1927).

Not long after its discovery,Scott (1892) suggested that Cory'sBittem might prove to be a colourmorph of the Least Bittem. Bent(1926) stated that "It now seems tobe generally conceded that the darkform ...is not a distinct species, but acase of melanism or erythrism."Cory's was removed as a species

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and placed on the Hypothetical Listin the Eighteenth Supplement to theAOU Check-list in 1923 and in thefourth edition of the Check-list in1931, because it was considered acolour morph of the Least Bittem(AOU 1923, 1931). AlthoughTavemer (1934) still listed Cory'sas a full species, interest in Cory'swaned because it was a colourmorph and it had all butdisappeared by that time.Interestingly, there is no mention ofCory's in the last two AOU Check-lists (AOU 1957, 1983). Cory'sLeast Bittem has gone from a fullspecies to a colour morph havingno taxonomic standing!

Morph GeneticsThere is no information in theliterature on the genetics of theCory's Least Bittem. Therefore, wecan only speculate about thepossible genetic basis of this morphand why it is so rare. Cory's LeastBittems seen today probably resultfrom a rare recessive allele in thepopulation of typical birds. Therecessive trait (Cory's) is maskedwhen paired with the dominant trait(typical). It appears only when twoof the recessive traits are paired bychance. Thus, Least Bittemsinheriting two copies (one fromeach parent) of the recessive allele(homozygous) would express theCory's colour morph. In birds,many morphological traits arecontrolled by more than one geneand intermediates are common; forexample, the colour morphs ofsome buteo hawks. The lack ofintermediate morphs betweentypical and Cory's Least Bittem

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28suggests a single gene having twoalleles for colour: dominant(typical) and recessive (Cory's).

Many Cory's specimens showtraces of albinism and melanism,which suggest inbreeding. O.E.Baynard reported in Bent (1926)that Cory's always paired withCory's and never with typical birds.This seems unlikely, but if true,suggests a strong positiveassortative mating (like with like)within the morphs. A male and afemale collected at Ashbridge'sBay, Toronto on 12 July 1900 isalso suggestive of assortativemating (Table I). Cory's LeastBittern may be an older form that isnow at a selective disadvantage andhas been replaced by the typicalmorph. The most likely explanationis that Ashbridge's Bay and LakeOkeechobee were the only placesknown where random processesallowed the Cory's morph tobecome temporarily established,because of chance colonization bya few individuals with the trait.

The almost completedisappearance of the Cory' s LeastBittern and the destruction ofAshbridge's Bay marsh areimportant losses of geneticdiversity and habitat to the LeastBittern.

Plumages, Molts, Ages and SexesLeast Bitterns molt twice a year.Juvenals (juveniles) undergo apartial molt in fall to first basic(first winter) plumage. Male andfemale first basic plumages (notseen in Ontario) resemble thejuvenal, but the back feathers havefew or no buff tips. First basic and


definitive basic (adult winter) birdsmolt much of their body plumage inlate winter and early spring intoalternate (breeding) plumage. Firstalternate and definitive alternateplumages are very similar. Thecrown and back have a distinctgloss. Breeding males in highalternate plumage have brightreddish-pink or carmine-pink at thebase of the lower mandible (JonDunn, pers. comm.). Alternate birdshave a complete molt from July toSeptember to definitive basicplumage. Definitive basic differsfrom alternate in both sexes in nothaving a strong greenish gloss tothe upperparts. Male, female andjuvenile Least Bitterns aredistinguishable in the field. See theillustrations of typical adult maleand adult female Least Bitterns onPlate 8 in Godfrey (1986) and male,female and juvenile on page 49 inScott (1987). For more informationon the molts and plumages of theLeast Bittern, see Bent (1926),Roberts (1955), Palmer (1962),Oberholser (1974), Cramp (1977)and Gibbs et al. (1992).

DescriptionSee Figures 1 to 3. Cory's LeastBittern is a combination erythristic(reddish) and melanistic (blackish)morph (Bent 1926, Cramp 1977). InCory's Least Bitterns, most of thebuff and white areas of typicalbirds are a rich chestnut. Some paleareas on typical birds (outerscapulars, wing tips and undertailcoverts) are replaced by black (notchestnut) in Cory's (Chapman1896). A few birds show moremelanism. Most individuals have

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Figure 1: Male Cory's Least Bittems (two left), male Least Bittems (middle and topright), female Cory's Least Bittem (bottom right). Drawing by Peter Burke.

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some (usually slight) albinisticplumage, especially on theabdomen and thighs (Chapman1896, Taverner 1934). The plumageof some individuals is acombination of erythristic,melanistic and albinistic markings!See the discussion in Chapman(1896); he provides a detailedcomparison of typical and Cory'sLeast Bitterns.

Bill Colour: In typical LeastBitterns the bill is mostly yellowwith a dark ridge, but in Cory's, thebill is mostly blackish brown.Information on bill colour is basedon specimen labels in the RoyalOntario Museum (ROM) and thedescription of the recent specimendescribed in Teixeira andAlvarenga (1985).

Adults: Adult males arechestnut with contrasting blackupperparts. The crown, hindneck,back and tail are black, with agreenish gloss in breedingplumage. The throat is a dark buffto chestnut, the foreneck ischestnut, the belly and flanks arechestnut or mixed with black, andthe undertail coverts are black. Theupper wing coverts are darkchestnut (not buff) and the winglinings are similar but paler. Adultfemales are similar to males but thecrown is slightly duller and theback is a flat blackish brown. Theundertail coverts are black in bothsexes. Cory's also lacks thecontrasting buffy wing patches(dark chestnut in Cory's) and thewhitish lines (black in Cory's) onthe outer scapulars of typical birds,giving it a more uniformly darkappearance to the upperparts at rest


and in flight. There is lessdifference between the sexes inCory's than in typical birds.

Juveniles: See Figure 2.Juvenile males and females showthe pattern of the adults but theyare paler and more uniform incoloration. They lack thecontrasting black areas, and theback and scapular feathers havebuffy tips. The undertail coverts areblackish brown in the juveniles.

Nestlings: See Figure 3. Basedon the colour of the down stillattached to juveniles in the ROM,the downy nestling plumage is adark buff in Cory's as opposed to acreamy buff in typical birds. In alarge quantity, this would make thedowny young darker than normal(Ross James, in litt.). James alsonotes, "I would expect the downyplumage to be darker in Cory's.This is what happens in the colourmorphs of the Reddish Egret andSnow Goose." The nestling Cory' sin Figure 3 is based on the aboveinformation. The statement in Bent(1926) that the downies are "coalblack" like young rails may be aslight exaggeration.

Eggs: Even the eggs of Cory'sare 'apparently darker than those oftypical birds (Palmer 1962). Theone egg labelled a Cory' s in theROM, collected by George Pearceon 15 June 1898 at Ashbridge'sBay, is slightly but distinctly darkerthan most Least Bittern eggs(Fleming 1901). This is the onlyCory's egg known. Given thedarkness of the birds at all ages, itis reasonable to expect the eggs tobe darker as the same pigments maybe involved. Note that the Cory's

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Figure 2: Juvenile Least Bittern (top), juvenile Cory's Least Bittem (bottom).Drawing by Peter Burke.

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egg is only a shade darker thannormal (noticeable in a series). Twosets of eggs in the ROM collectedat Ashbridge's Bay in 1890 and1891 during the Cory's period aresimilar in colour to the singleCory's egg. However, Ross James(pers. comm.) cautions that theseeggs may be from typical birds andFleming (1901) reported seeing aset from typical birds as dark as theCory's egg.

Intermediates: A possibleintermediate between a typical anda Cory's Least Bittern in the ROM(#67405) was collected in earlySeptember 1905 near Guelph,Wellington County. It is listed as aCory's in one ROM file. It was notsexed but appears to be a male. Theneck and underparts are acinnamon buff, not a rich chestnutlike a Cory's; however, the rest ofthe plumage closely matches atypical Least Bittern. It is not aCory's in our estimation. This birdmay be dyed, stained with iron, or arichly coloured typical LeastBittern.

Cory's number 20 in Table 1 islike the others in the ROM, exceptthe wing panels are somewhatintermediate between buff (typical)and dark chestnut (Cory's).

An injured Cory's Least Bitternwas photographed and released inOhio in 1949. See number 9 belowunder the heading of sight records.Regarding this latter bird, CraigCampbell (in litt. to R.T. Peterson1983) wrote "While I quite agreethat the bird in question is a Cory's,I note by comparison with somepaintings of adult males of thisentity that there are a few slight


differences. Some of these lie in thelightness of the bill, cheeks, neckand wing patches of the bird in thephotograph.' ,

A road-killed bird from thecauseway at Long Point in 1981was originally thought to be aCory's Least Bittern. When RogerTory Peterson examined thespecimen in 1982, there was debatewhether it was a Cory's or a richlymarked typical Least Bittern. Somethought it might be an intermediate.It later proved to be a typical LeastBittern in juvenile plumage. Thespecimen is now missing (DavidAgro and Jon McCracken, pers.comm.). The juvenile plumage ofthe Least Bittern was not well-known until it was illustrated in theNational Geographic Guide (Scott1983, 1987). Roberts (1955)describes considerable variation injuvenile Least Bitterns.

A few Cory's show extensivewhite feathering on the underparts.These are partial albinos, notintermediates.

In summary, Chapman (1896)found no evidence of intermediatesbetween Cory' s and typical LeastBitterns. Since then, there is stilllittle evidence of the existence ofany truly intermediate plumages. Itappears that both Cory's andtypical Least Bitterns show someindividual variation.

Note: The illustration labelledan "ad dark morph" ( number 4 onPlate 30) in Cramp (1977) does notcorrespond to the description in thesame book. It is definitely not aCory's or even a typical LeastBittern.

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Figure 3: Nestling Least Bittern (left), nestling Cory's Least Bittern (right).Drawing by Peter Burke.

Field IdentificationCory's is much darker than atypical Least Bittern. See Figures 1to 3. Adults are black (males) orblackish (females) above and a richchestnut below. At rest and inflight, they lack the contrastingbuff wing patches and whitish lineson the outer scapulars of typicalbirds. In flight, adult Cory's isalmost uniformly blackish aboveand chestnut below, appearing verydark. A Cory' s skulking in a marshis almost like a blackbird at times.Juveniles are also very dark, butmore uniform in coloration.Caution: See Figure 1. Observerswho are not familiar with the

juvenile plumage of typical LeastBitterns might confuse it with aCory's. Typical juveniles aredrabber and more uniform thanadults with less contrastingshoulder patches. See thephotograph of a juvenile LeastBittern on page 5 in Wormington(1985). This photograph shows whyit could be confused with a Cory'sLeast Bittern. However, Cory's is amuch darker bird at all ages and themoment you see one there shouldbe no doubt about its identity! Also,novices might confuse the darkjuvenile Virginia Rail or even aGreen Heron as a Cory's LeastBittern.

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DistributionSpecimens: Palmer (1962) lists 31specimens taken between 1885 and1914 as follows: Ontario (16, seeadditions below), Florida (7),Michigan (2), lllinois (2), NewYork (1), Ohio (1), Massachusetts(1) and Wisconsin (1). There is arelatively recent specimencollected in Brazil on 13 May 1967.It is the first record of the Cory'smorph in the range of the SouthAmerican subspecies I.e.erythromelas (Teixeira andAlvarenga 1985).

The first nests were found inFlorida in 1890 and Ontario in1898. Lake Okeechobee, Floridaand Toronto, Ontario are the onlyconfirmed breeding locations.

See Table 1 for a list of Ontariospecimens. The following providesadditional information on many ofthe specimens listed in Table 1.Palmer (1962) cites 16 specimensfrom Ontario, but there are at leastsix others discussed below.Mcllwraith (1894) mentions thediscovery of the first Ontariospecimen on 18 May 1890 atAshbridge's Bay, Toronto. Thisspecimen is now missing from theRoyal Ontario Museum (RossJames, pers. comm.). Fleming(1902) reports 16 specimens fromToronto, perhaps the same 16reported above by Palmer (1962).Currently in the Royal OntarioMuseum, there are 13 specimens(another is missing) and one eggfrom Ontario. All the Torontospecimens listed in Table 1 and theegg are from the formerAshbridge's Bay marsh, Toronto.

The only specimen not from


Toronto in the ROM was shot byDayton Murphy about June 1895 atthe east end of West Lake nearWellington (Hallowell) in PrinceEdward County (Fleming, undated;Baillie 1935 letter in ROM; Snyder1941; Sprague and Weir 1984).Two specimens from Toronto are inBritish museums and one was soldto a collector in Maine (Fleming1902). Three specimens fromToronto are in the AmericanMuseum of Natural History (ROMfiles).

In addition, there is a femaleCory's Least Bittem in theCanadian Museum of Nature takenby C.H. Young at Point Pelee on 5June 1913 (Michel Gosselin, pers.comm.). About the Pelee bird, P.A.Tavemer wrote to J.H. Fleming on 2October 1935, "I was paddling theboat when Young shot the Cory' sBittem. It got up at ordinary rangeabout as other Least Bittems didand I told him to shoot quickly. Onecould not say that it wasparticularly wild or tame" (ROMfiles). The Point Pelee and PrinceEdward County specimens taken inJune suggest breeding at theselocations.

A note in the manuscript filesof the Canadian Museum of Naturefrom J.H. Fleming dated 27November 1935 mentions aspecimen from Toronto owned bythe University of Toronto Schools(UTS). Jim Baillie repeatedly triedto get this specimen for the ROM,but was unsuccessful (AlexCringan, pers. comm.). About theUTS specimen, John A. Livingstonwrote, "This was a mounted Cory's- old and badly eroded - that

teetered in an ancient glass case inthe high school I attended. This wasa significant bird, and it deservedmore appropriate quarters; in thecourse of time James Baillie, of theRoyal Ontario Museum, persuadedmy biology teacher to donate it tothe R.O.M.'s distinguishedcollection. Regrettably, ourheadmaster learned of thearrangement and immediatelyvetoed it. After all these years, Ihave no idea where that rarespecimen eventually came to rest;perhaps it has served to inspiresubsequent generations ofschoolboys" (Landsdowne andLivingston 1968). This specimenwas missing when we checked themounted specimens at the UTS on26 March 1996.

Possible additional specimensfrom Toronto not included in Table1 are listed in ROM files: In 1925,George Pearce told Jim Baillie thathe sent specimens of Cory's LeastBitterns to the South KensingtonMuseum in England; one to WalterRothschild in New York City; oneto William Brewster in Boston; oneto Barnes in Tiffin, Ohio; one toWilliam Owen (Toronto"), one hestill owned at the time; and therewas one in a case at 51 JackmanAve., Toronto. The Barnes andBrewster specimens are possibleadditions to Table 1. A few moreCory's Least Bitterns may exist inprivate collections or museums.

There are parts of two wings inthe ROM files from a bird claimedto be a Cory' s that was foundcrushed and rotting on thecauseway at Long Point on 4September 1955. However, the

35buffy wing coverts and rest of thewings match a typical Least Bittern.Specimen number 67405 in theROM is listed as a Cory's in onemuseum file, but is not one in ouropinion. See the discussion aboveunder the heading of intermediates.

Cory's Least Bitterns wereprized by early collectors. Anewspaper story in the TorontoTelegram of 31 July or 1 August1913 tells the story of a boy whosold a Cory's Least Bittern to aToronto taxidermist for 25 cents.After mounting it, the taxidermistsold the Cory's to merchantmillionaire and bird collectorWalter N. Rothschild of New YorkCity for 100 dollars. This would bemore than 2000 dollars today!George Pearce, who collected manyLeast Bitterns at Ashbridge's Bay,was said to have destroyed manynormally coloured Least Bitterns tohide the fact that Cory's was acolour morph, thus helping tomaintain an inflated price (RossJames, per ROM files). Jim Baillietold Gerry Bennett (pers. comm.)that George Pearce, known as theHermit of the Humber, collectedtypical Least Bitterns, dyed themred, and sold some as Cory's tounsuspecting collectors. One ofthese dyed birds apparentlysurfaced in the 1950s. Earl Godfrey(pers. comm.), Curator Emeritus ofbirds at the Canadian Museum ofNature, was sent a specimen of a'Tory's Least Bittern" to examine.Godfrey determined that it was nota Cory's, but a typical Least Bitterndyed to look like one!

The total number of Cory'sLeast Bitterns collected in Ontario

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is at least 22, of which 20 are fromToronto, plus one from Point Peleeand one from Prince EdwardCounty. Adding the 15 specimensfrom the United States (Palmer1962) and the one from Brazil(Teixeira and Alvarenga 1985), thetotal number from all locations is atleast 38!

Sight Records: There arenumerous sight records includingrecent ones for Ontario andelsewhere. (1) Paul Harrington sawone about 1921 in Toronto (ROMfiles). (2) A. C. Bent and M.Copeland saw a Cory's on 7 April1925 in Pinellas County, Florida(Bent and Copeland 1927). (3) Onewas seen I August 1927 atAshbridge's Bay, Toronto (ROMfiles). (4) One was seen by PeggyMitchell on 6 July 1932 at Erindale(ROM files). (5) George Pearcetold Jim Baillie of the ROM that hefound Cory's breeding in 1923 atPort Rowan on Lake Erie, NorfolkCounty (ROM files). (6) One wasseen by Alex Lucas on 2 August1939 along the Otonabee River atRice Lake, Peterborough County. Itwas described to Jim Baillie as"chocolate coloured all over"(ROM files). (7) James Savageobserved a Cory's Least Bittem atLong Point, Norfolk County on 16September 1928 (Snyder andLogier 1931). (8) George North andWilliam Campbell saw a Cory' s inHamilton on 10 August 1941 (ROMfiles; Bob Curry in Litt.). (9) RogerTory Peterson (in Litt. to CraigCampbell 1982, 1983) was given acolour photograph of a Cory' sLeast Bittem taken in Ohio in 1949.The date stamped on the


photograph is 3 October 1949. Thisbird flew into a building atYoungstown in the autumn of 1949and was photographed by Frank F.Ferris who apparently gave thephotograph to Peteeson. ThisCory's was later released (DuaneFerris, pees. comm.). (10) W.e.Mansell saw a Cory's on 21 May1950 at the third Humber Rivermarsh, Toronto. (11) Gerry Bennett(pees. comm.) saw a Cory's nearHamilton in the 1950s. (12) DonSutherland (pees. comm.) and NickGodfrey flushed a Cory's LeastBittem in May 1973 at Hanlan'sPoint on the Toronto Islands, notfar from the former stronghold atAshbridge's Bay. (13) The mostrecent Ontario report is from CraigCampbell (pers. comm.) and DavePerrin who attracted a Cory's to thetaped call of a Least Bittem inPrince Edward County in July 1981.The behaviour noted in the lastsighting is further evidence thatCory's is indeed a colour morph,rather than a distinct species. Thereare no doubt other sight recordsthat we missed.

Ashbridge's BayToronto's Ashbridge 's Bay marshwas the world's centre ofabundance of the Cory' s LeastBittem. More specimens of Cory'swere taken at Ashbridge's Bay(between 1890-1900) thananywhere else in the world, and itwas recorded breeding there in1898 (Ames 1901; Fleming 190 I,1906, undated). Ashbridge's Bayand the Lake Okeechobee region ofFlorida were the only confirmedbreeding locations of Cory's Least

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Table 1: Cory's Least Bittern - Ontario Specimens

*Age\Sex Date Location Collection

I. adult male 18 May 1890 Toronto ROM**2. adult female 20 May 1893 Toronto BM3. adult male 26 May 1894 Toronto ROM4. adult female 16 July 1894 Toronto AMNH5. adult male 16 Aug. 1894 Toronto ROM6. juvenile male 17 Aug. 1894 Toronto ROM7. juvenile male 24 Aug. 1894 Toronto ROM8. adult male about 1895 Toronto UTS**9. adult male 17 Aug. 1896 Toronto AMNH

10. adult male 14 May 1897 Toronto AMNHI I. adult female 30 June 1897 Toronto ROM12. adult male 8 June 1898 Toronto Private USA13. adult female 15 June 1898 Toronto ROM14. juvenile male 3 Aug. 1898 Toronto ROM15. adult male 7 Aug. 1899 Toronto ROM16. juvenile male 14 Aug. 1899 Toronto ROM17. adult male 8 Sept. 1899 Toronto BM18. adult male 21 Sept. 1899 Toronto ROM19. adult male 12 July 1900 Toronto ROM20. adult female 12 July 1900 Toronto ROM21. adult female ? June 1895 Prince Ed. Co. ROM22. adult female 5 June 1913 Point Pelee CMN

AMNH - American Museum of Natural HistoryBM - British MuseumCMN - Canadian Museum of NatureROM - Royal Ontario MuseumUTS - University of Toronto Schools• - Some "adults" are likely in first alternate or definitive basic plumage** - Specimen missing

Total Specimens: World 38 (Ontario 22, United States 15, Brazil I)

Sources: ROM Collection, Ross James, pers. comm.;CMN Collection, Michel Gosselin, pers. comm.;Chapman (1896); Flerning (1902); Palmer (1962);Teixeira and Alvaarenga (1985).

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Bittern, but it undoubtedly bredelsewhere.

Early ornithologists regardedAshbridge's Bay marsh as one ofthe finest marshes in Canada. Themarsh covered some 560 hectares(1385 acres). We are indebted toGeorge Fairfield (in prep.) forpermission to quote from hisupcoming book on Ashbridge'sBay, to be published by the TorontoOrnithological Club: "The marshwas formed at the delta of the DonRiver. It was enclosed on the southside and separated from LakeOntario by a long peninsula of sandwhich continued on to form what isnow Toronto Islands. The presentToronto shoreline in this areafollows roughly the south edge ofthis peninsula. The peninsula wasformed by the deposition ofmaterial eroded from theScarborough Bluffs and carriedwestwards by lake currents."

Ashbridge's marsh wasdescribed by Hubert Brown in 1894(Fleming 1894, Fleming undated)."The marshy location to which thebirds resort, and where all the sevenwere taken, is only half a milesquare, protected from the seas ofLake Ontario by a narrow sand-bara few yards in width, and is situatedimmediately adjacent to the city ofToronto. A great deal of shooting ispracticed there at all seasons, sothat the bird, though of retiringhabits, could scarcely have chosena more frequented piece of marsh."

Ashbridge's Bay marsh is gonenow, the result of early filling todevelop a harbour and later asewage treatment plant for Toronto.The marsh was mostly destroyed


when Taverner published Birds ofCanada in 1934. Remnants of themarsh existed into the 1960s.Regardless, the collecting pressurein one decade (1890-1900)virtually eliminated the Cory'sLeast Bittern from Ashbridge's Baylong before the marsh itself haddisappeared.

SummaryThe Cory's Least Bittern is a veryrare colour morph of the LeastBittern. In Cory's, the buff andwhite areas of the typical form arereplaced by chestnut to chocolate.Ashbridge's Bay marsh (now gone)in Toronto was the formerstronghold of the Cory's LeastBittern in the world. Most of theknown specimens from throughoutits range date from 1885 to 1914,with a more recent specimen fromBrazil in 1967. The total number ofknown specimens is 38 of which 22are from Ontario. There wereOntario sightings in 1973 and 1981.

If our ideas about the geneticsare correct (homozygousrecessive), it is likely that Cory'sLeast Bitterns will turn up fromtime to time. Landsdowne andLivingston (1968) said, "Themysterious chestnut bird shouldstill be watched for, wherever thereare least bittems. Some may remainat Lake Okeechobee, Florida, or inthe Long Point marshes of LakeErie." The Ontario Bird RecordsCommittee is interested in recentreports of Cory's Least Bittern.

AcknowledgementsWe are grateful to the followingpeople: David Agro and the

Academy of Natural Sciences ofPhiladelphia, Gerry Bennett, FredBodsworth, Dawn Brenner, CraigCampbell, John Cranmer-Byng,Alex Cringan, Bill Crins, BobCurry, Jim Dick, Bruce Di Labio,Jon Dunn, George Fairfield, DuaneFerris, Earl Godfrey, MichelGosselin and the Canadian Museumof Nature, Robert Harlan, Jean Iron,Ross James and the Royal OntarioMuseum, Alvaro Jararnillo, HarryKerr, Tony Lang, Barry KentMacKay, Rory MacKay, JonMcCracken and the Long Point BirdObservatory, Stan Pearl and theUniversity of Toronto Schools,Murray Speirs, Don Sutherland andthe Natural Heritage InformationCentre, Ron Tozer, and MikeTurner. Ross James and staff at theROM were very helpful in allowingus to examine specimens and thefiles of James H. Fleming andJames L. Baillie. Jon McCrackenkindly loaned us photographs oftypical Least Bittern nestlings. Weare indebted to George Fairfield forinformation from his upcomingbook about Ashbridge's Bay. BarryKent MacKay kindly gave uspermission to use his Cory's LeastBittern illustration from George'sbook on the cover of Ontario Birds.

Literature CitedAmerican Ornithologists' Union. 1895.

Check-list of North American Birds 2ndEdition. American Ornithologists' Union,New York.

American Ornithologists' Union. 1923.Eighteenth Supplement to the AmericanOrnithologists' Union Check-list of NorthAmerican Birds. Auk 40: 513-525.

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American Ornithologists' Union. 1931.Check-list of North American Birds, 4thEdition. American Ornithologists' Union,Lancaster, Pennsylvania.

American Ornithologists' Union. 1957.Check-list of North American Birds, 5thEdition. American Ornithologists' Union,Washington, D.C.

American Ornithologists' Union. 1983.Check-list of North American Birds, 6thEdition. American Ornithologists' Union,Washington, D.e.

Ames, J.H. 1901. Nesting ofCory's Bittern(Ardetta neoxena) and other notes. Auk18: 106-107.

Bent, A.C. 1926. Life Histories of NorthAmerican Marsh Birds. United StatesNational Museum Bulletin 135,Washington, D.e.

Bent, A.C. and M. Copeland. 1927. Notes onFlorida birds. Auk 44: 376.

Chapman, F.M. 1896. The standing ofArdetta neoxena. Auk 8: 10-19.

Choate, E.A. 1985. The Dictionary ofAmerican Bird Names. The HarvardCommon Press, Harvard and Boston,Massachusetts.

Cory, C.B. 1886. Description of a new NorthAmerican species of Ardetta. Auk 3: 262.

Cramp, S. (editor). 1977. Birds of the WesternPalearctic: Handbook of the Birds ofEurope, the Middle East and North Africa.Volume I: Ostrich to Ducks. OxfordUniversity Press, London.

Fairfield, G. In prep. Ashbridges Bay. TorontoOrnithological Club, Toronto.

Fleming, J.H. 1894. Ardetta neoxena atToronto. Biological Review of Ontario I:85.

Fleming, J.H. 1901. Nesting of Cory's LeastBittern at Toronto, Ontario. Auk 18: 106.

Fleming, J.H. 1902. Cory's Bittern. Auk 19:77-78.

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Fleming, J.H. Undated. The standing of Cory'sLeast Bittern, Ixobrychus neoxenus (Cory).Unpublished manuscript in the RoyalOntario Museum, Toronto.

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Ron Pittaway, Box 619, Minden, Ontario KOM 2KOPeter Burke, Box 1092 , Lakefield, Ontario KOL 2HO


f! - jean iron · 26 recognizable forms cory's least bittern by ron pittaway and peter burke...

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