51 The Status of Colonial Waterbirds Nesting at , Lake , 1959-1987

by Rob Z. Dobos,john Struger, Hans Blokpoel and D.V. Chip Weseloh Hamilton Harbour, Regional years. Municipality of Hamilton­ Hamilt.on Harbour is separated Wentworth, located at the west.ern from Lake Onl.ario by a large sand­ end of Lake On tario, is home to bar, the Burlington Reachstrip what may be the most diverse (Figure 1). Landfi lIing has been colony of waterbirds on the carried out on the Harbour side of . Seven the Reachstrip south of the species of colonial waterbirds, the Burlington Beach Canal by the Double-crested Cormoran t Hamilton Harbour Commissioners (Phalacrocorax au'Titus) , Snowy Egret (HHC) over the past 30 years to cre­ (Egretta thula) , Black-crowned ate the present Confined Disposal Night-Heron (Nyctiwrax nycticarax) , Facility (CDF) , for containment of Ring-billed Gull (LaTUS delawaren­ harbour dredged sediments, and sis), Herring Gull (L. argenlalus) , the Pier 25, 26 and 27 pon facilities Caspian Tern (Sterna caspia) and (Figure I). The berms and filled Common Tern (S. hirundo) , nested cells of the CDF have provided a rel­ there in 1986. The purpose of this atively isolated site for the nesting paper is to document the numbers of colonial waterbirds since the mid­ of these species which have nested 1970s. at Hamilton Harbour in recent

Rob Z. Dobos, Canadian Wildlife Service. Present address: 1319 Book Rd. W., R.R. #1 ,jerseyville, Ontario LOR IRO. john Struger, Canadian Wildlife Service. Present address: 269 Wexford Ave. S., Hamilton, Ontario LBK 2P1. Hans Blokpoel, Canadian Wildlife Service, 1725 Woodward Dr., , Ontario KIA OE7. D. V. Chip Weseloh, Canadian Wildlife Service, P.O. Box .=5050, 867 Lakeshore Rd., Burlington, Ontario L7R 11\6.

VOLUME 6 NUMBER 2 52

BURLINGTON 500 0 500 m I •••• , ,

FARRE ISLANDS NEARE ISLAND \. tN HAMILTON HARBOUR

EXTENT OF WATERBIRD COLONIES IN 1987 CJ

ST£:LCO

HAMILTON

(j.",ON' ~ PARKDALE ~ ,nEl WO.K'V

Figure 1: Location of waterbird colony site on Hamilton Harbour, Lake Ontario

ONTARIO BIRDS AUGUST' 1988 53

The flat earth and rubble sub­ DQ'Ub~CTestedQmnorant strate which is largely unvegetated Double-crested Cormorants (DCC) has proven suitable for the nesting first nested in Hamilton Harbour in of Herring and Ring-billed Gulls 1984, when one nest was found on and Common and Caspian Terns. A the ground. The number has since small grove of Eastern Cottonwood risen to 51 nests in 1987, all in trees (POPUlusdeltoides) trees on the (Table 1). The cormorants nested northwest end of the site has sup­ in the upper branches of the cot­ ported a colony of Black

VOLUME 6 NUMBER 2 54

Table 1: Colonial waterbird populations nesting on Hamilton Harbour, 1959-1987

Year Double- Snowy Black- ~- Herring Caspian Common crested Egret crowned billed Gull Tern Tem Cormorant Night-Heron Bull

1959 0 0 15c 0 0 0 - 1961 0 0 - 2f 0 0 '!Jf 1966 0 0 - 0 0 0 66f 1967 0 0 - 0 0 0 8'!Jf 1968 0 0 - 0 0 0 79f 1970 0 0 - 0 0 0 +.\ 1971 0 0 - 0 0 0 95". 1972 0 0 - 0 0 0 150ft 1973 0 0 - 0 0 0 42ft 1975 0 0 6d 0 0 0 0 1976 0 0 - 0 7j 0 0 1977 0 0 - 0 14, 0 0 1978 0 0 - 17A - 0 0 1980 0 0 1, '!J29i 102, 0 0 1981 0 0 19, 2400i 1M, 0 0 1982 0 0 l'!Jf 5000f 50f 0 +g 1984 1a 0 51a 11224i 202, 0 +g 1985 2a 0 98g 1'!J778, 150g 0 225g 1986 14a Ib 18'!Ja 16000, 106, 48, +4 1 1987 51a 0 212a 21207, 225, 1M, 55'!J,

- No data available g Lamond (1985) + Nesting, but not censused North (1978) a L Simser, pers. comm. "i Blokpoel and Tessier (1986) b Curry and Bryant (1987) j Blokpoel (1977) c North (1959) Ie Gilbert!On (1975) d North (1975) ". Morris et al. (1976) , CWScensus ft Morris and Hunter (1976) f Ontario Nest Record Scheme

branches of the cottonwood trees , Lake Ontario). (Figure 2). Sufficient nesting sites Such a situation could also occur at , appear to be available for future the Hamilton Harbour colony. increases in nesting birds. However, The earliest record of BCNHs BCNHs are know to desert their nesting in the Hamilton Harbour colony site iflarge numbers of area was of three nests in 1936 at DCCs nest above them in the same Van Wagner's Beach,just east of the trees (e.g., at Pigeon Island, harbour (Sheppard 1944).

ONTARIO BIRDS AUGUST 1988 55

Anothern BCNH colony was locat­ early 1970s and at present the ed in a grove of trees on an old species appears to be expanding its inlet on the southeast shore of the range within the province harbour behind the Firestone (Goodwin 1987). factory. Fifteen nests were reported there in 1959 (Table 1). This colony Ring-billed GuU was substantially larger before this The Ring-billed Gull (RBG) was time and was believed to have num­ first reported nesting on Hamilton bered over 100 nests during the Harbour in 1961, with nests being 1950s (R Curry, pers. comm.). found along the south shore of The Hamilton Harbour BCNH Windermere Basin, behind the colony was the second largest on Parkdale Steel Works (ONRS western Lake Ontario in 1987. A 1961a). It was not recorded again colony at Tommy Thompson Park until 1978, when 17 nests were (Leslie Street Spit), Metropolitan recorded at the CDF (Table 1). , numbered 591 nests in Numbers increased rapidly to 1987 (Blokpoel, unpubl. data). A approximately 2,400 in 1981, colony on a small island in the 11,224 in 1984 and 21,207 in 1987 directly above the at the CDF site (Table 1). RBG's Horseshoe Falls, Regional have experienced rapid population Municipality of Niagara, had 155 growth throughout the entire Great nests in 1987, while a colony at Lakes. The Great Lakes RBG popu­ Mugg's Island in , lation has more than doubled from Metropolitan Toronto, had more 1976 to 1984, with an average annu­ than 50 nests in 1986, but was al growth rate of 11 % (Blokpoel deserted in 1987 (E. Machell, pers. and Tessier 1986). On Lake comm.). Data from the Ontario Ontario, the saturation of nesting Breeding Bird Atlas (Cadman et al. sites at several colonies, succession­ 1987) indicate that only five al increases in vegetation (reducing colonies in Ontario had more than the amount of available nesting 100 nests during the period 1981­ habitat) and control programs to 85, those being at Middle Island deter nesting at the Tommy and EastSister Island, Essex Thompson Park and Mugg's Island Coun ty, in western , colonies in Toronto most likely con­ Nottawasaga Island, , tributed to the rapid increase at the in southern and Hamilton colony. Available nesting Mugg's Island and Tommy sites are still abundant on the filled Thompson Park, Metropolitan cells of the CDF, depending on Toronto (Goodwin 1987). The plans by the HHC to develop the BCNH population has fluctuated site (Figure 3). considerably in Ontario over the The Hamilton Harbour RBG last 50 years. It has recovered from colony was the fifth largest on all of low numbers during the 1960s and Lake Ontario in 1984. Colonies at

VOLUME 6 NUMBER 2 56

Little Galloo Island, Tommy periphery ofthe RBGs. Thompson Park, Gull Island and The Herring Gull has been High Bluff Island, Northumberland shown to be the mostwidespread County, as well as at the Port breeding species in Ontario Colborne mainland, Regional (Cadman et al. 1987). In recent Municipality ofNiagara, (the years, its population has been slowly largest on Lake Erie and within increasing on Lakes Ontario and close proximity to Hamilton Huron (Weseloh et aL 1987). The Harbour) were larger than the Hamilton Harbour colony is one of Hamilton Harbour colony in 1984 the largest on western Lake (Blokpoel and Tessier 1986). Ontario, with other large colonies being located at Tommy Thompson Herring Gull Park in Toronto, Scotch Bonnet Herring Gulls were first recorded Island and Gull Island near nesting at Hamilton Harbour in Brighton, above the Horseshoe Falls 1976, when 7 nests were counted on the Niagara River, and on the (Table 1). By 1980 the number had PortColborne breakwall. risen to 102 (Table 1). Since 1984 the number of nests has remained Common Tern fairly stable, with 225 nests counted The first reported nestings of in 1987 (Table 1). The Herring Common Terns in the Hamilton Gulls nest mostly at the northern area were in 1946 (15 nests) and end of the waterbird colony, along 1949 (two nests) (North 1972). The the connecting dykes and along the first record ofCommon Terns nest-

Figure 2 Double

ONTARIO BIRDS AUGUsr 1988 57 ing specifically on the Harbour was induced by toxic chemical bioaccu­ in 1961, when three nests were mulation (Morris and Hunter found on the south shore of 1976). Common Terns did not sub­ Windermere Basin behind the sequently nest on the Harbour un til Parkdale Steel Works (ONRS 1982 (Lamond 1985). Numbers 1961a). Nesting was first reported have since increased to a total of at the Hydro Islands in 1966, with 553 nests in 1987 (Table 1). Of 66 nests recorded (ONRS 1966). these, 151 were located at the Pier Nesting occurred at the Hydro 27 site adjacent to the RBG colony. Islands up to 1972 inclusive (ONRS The only other Common Tern 1967; ONRS 1968; Gilbertson 1975; colony on western Lake Ontario is Morris et aL 1976). In 1971 one at Toronto's Tommy Thompson Common Tern nest was also found Park, which historically supported at the Pier 27 CDF site (ONRS over 1000 nests, but in 1987 had 1971) . In 1973 the terns nested (42 only 332 nests. Data from the Atlas nests) on the mainland shoreline ofthe Breeding Birds ofOntario indi­ adjacent to the islands due to inun­ cate that less than 5% of the 123 dation of the islands resulting from 1Ox10 km squares in which record high water levels (Morris Common Tern breeding was and Hunter 1976). A year later this confirmed had more than 100 nests colony was deserted, probably due (BlokpoeI1987b). Hamilton to the combined effects of the loss Harbour is, therefore, a major nest­ of nesting habitat and several years ing area for Common Terns in the of reduced reproductive success province. Other Common Tern

VOLUME 6 NUMBER! 58

colonies in the vicinity ofHamilton the RBG colony. All Caspian Tern and the number ofnests ateach in colonies in Ontario are associated 1987 were as follows: 1~~1 at Port with nesting RBGs (Blokpoel Colborne breakwall (R.D. Morris, 1987a). The only other Caspian pers. comm.); 157 on the Niagara Tern colony on western Lake River [Tower Island, Far Crib, Near Ontario is at the Tommy Thompson Crib and Buckhorn Weir] (G. Park, which has decreased from 197 Batcheller, pers. comm.); and 496 nests in 1985 to 45 nests in 1987. at Buffalo, New York [Donnelly's The rapid growth ofthe Hamilton Pier, ReefLighthouse and Short colony may be attributed to immi­ Breakwater] (G. Batcheller, pers. gration ofdisplaced birds from the comm.). Toronto colony. The Caspian Tern is considered rare in Ontario and Caspian Tern Canada (BlokpoeI1987a), thus the Caspian Terns have nested at Hamilton colony is significant Hamilton Harbour since 1986, provincially and nationally. when 48 nests were counted. In 1987, the number increased sub­ Future of the Pier 27 stantially to 1M nests (Table 1). colonies These birds nest in an area within Over the last decade, the colonial waterbird nesting area at Pier 27 has become one of the most impor­ tant nesting sites on the Great Lakes, with populations ofbirds that are regionally, provincially or nationally significanL There is only one other colony site on the Canadian Great Lakes that has had as many as seven spiecies nesting as did Hamilton Harbour in 1986. Seven colonial waterbird species nested at the Tommy Thompson Park in 1982: BCNH, RBG, Herring Gull, Common Tern, Caspian Tern, Great Black-backed Gull (LaTUS marinus) and California Gull(L. ca~ ifarnicus) (Fraser 198~). Both of these colonies have become estab­ lished on man-made sites. Very little suitable nesting habitat for colonial waterbirds existed on the Harbour Figure 3: Ring-billed Gull nesting habi­ prior to the 1970s. However, the tat, Pier 27, Hamilton Harbour. future of the Pier 27 site is not Photo by Hans Blo1cpoeL

ONTARIO BIRDS AUGUsr 1988 59 secure, due to eventual develop­ because, apart from the two small ment plans for port and industrial Hydro Islands, there are presently facilities by the lllIC. no other suitable nesting sites in The lllIC has recognized the the Harbour. In order to prevent ecological significance of the site to this loss of valuable and interesting some degree, by allowing most of waterbird colonies, alternative nest­ the nesting area to remain undUr ing habitat in Hamilton Harbour turbed until it is required for devel­ could be built and maintained for opment in approximately 15 years. optimal use by a diversity of colo­ Thus, the short-term prospects for nial waterbird species. HHC might the colonies look promising. In be interested in greatly enlarging fact, it is likely that Ring-billed Gulls the Hydro Islands or in construct­ will continue to increase rapidly in ing new islands in Hamilton numbers, and in the process are Harbour. Those islands could then likely to encroach upon, or com­ be managed for colonial waterbirds pletely usurp the nesting areas of by a local naturalist group (e.g., the Common and Caspian Terns. The Hamilton Naturalists' Club with RBGs arrive several weeks before assistance from CWS). In fact, the the terns do, and their burgeoning Hamilton Harbour Remedial numbers are likely to overtake the Action Plan (RAP) for the clean-up nesting areas of the terns. One of Hamilton Harbour is at present technique to prevent this encroach­ considering a proposal to encour­ ment and to maintain nesting habi­ age the birds now nesting at the tat for Coriunon Terns is to exclude CDF to move to an expanded gulls by installing wires or Hydro Island site. monofilament early in the season. The gulls tend to avoid the 'wired' Acknowledgements area, while terns can sometimes be We would like to thank those induced to nest beneath the wires. ornithologists who have provided To prevent ~Gs from completely their data on nesting waterbirds on taking over the tern colonies at the the Great Lakes, and historical two Hydro Islands, CWS has already information, including Len Simser discouraged colonizing gulls by (Royal Botanical Gardens), Gaston destroying their eggs (under CWS Tessier (Canadian Wildlife Service), permit) in recent years. Robert Curry (Hamilton Although the short-term Naturalists' Club) and Eric Machell prospects for the Pier 27 colonies (Toronto Bird Observatory). Also, are reasonably good, the colonies we thank the Hamilton Harbour are most likely to disappear once Commissioners for permitting CWS Pier 27 is further developed into an to census waterbirds nesting on operational harbour facility. The their site. displaced birds would probably move out of Hamilton Harbour

VOLUME 6 NUMBER·2 60

literature Cited North, G. W.1972. Unpublished ornithological BloItjlO6~ H. 1977. Gulls and terns nesting in records, 1925-1972. Department of northern Uke Ontario and the upper St. Ornithology, Royal Ontario Museum, Lawrence River. Can. Wild!. Serv. Prog. Toronto. Note No. 75. North, G. W.1975. Noteworthy bird records. BloItjlO6~ H. 1987a. Caspian Tern. I'll Cadman, Wood Duck 29:31. M.D., P.F.J. Eagles and F.M. Helleiner. North, G. W. 1978. Noteworthy bird records. 1987. Atlas ofthe Breeding Birds of Wood Duck 32:29. Ontario. University ofWaterloo Press, Ontario N~t RIcordScJwmut. 1961a. Nest record Waterloo, Onto card for Common Tern in Wentworth BloItjlO61, H. 1987b. Common Tern. I'll County. Department ofOrnithology files, Cadman, M.D., P.F.J. Eagles and F.M. Royal Ontario Museum, Toronto. Helleiner. 1987. Atlas ofthe Breeding Ontario NlSt RIcord ScJIimw. 1961b. Nest record Birds ofOntario. University ofWaterloo card for Ring-billed Gull in Wentworth Press, Waterloo, Onto County. Department ofOrnithology files, BloItjlO6~ H. and G.D. T~sVt: 1986. The Ring­ Royal Ontario Museum, Toronto. billed Gull in Ontario: a review ofa new Ontario N~t RIcord ScNmut. 1966. Nest record problem species. Can. Wild!. Serv. Occas. card for Common Tern in Wentworth Pap. No. 57. County. Department ofOrnithology files, Cadman, M.D., RFJ Eagl8s and F.M. Helleinlf'/. Royal Ontario Museum, Toronto. N~t 1987. Atlas ofthe Breeding Birds of Ontario RIcord ScNmut. 1967. Nest record Ontario. University ofWaterloo Press, card for Common Tern in Wentworth Waterloo, Ont. County. Department ofOrnithology files, Curry, R. and G.D. Bryant. 1987. Snowy Egret: Royal Ontario Museum, Toronto. a new breeding species for Ontario and Ontario N~t Record ScNmut. 1968. Nest record Canada. Ontario Birds 5:64-67. card for Common Tern in Wentworth &ologistics LimiUd. 1976. Hamilton-Wentworth County. Department ofOrnithology files, Region Environmentally Sensitive Areas Royal Ontario Museum, Toronto. Study. Hamilton Region Conservation Ontario NlSt RIcord ScNmut. 1971. Nest record Authority. card for Common Tern in Wentworth Fraur, D.M. 1983. Breeding birds as indicators County. Department ofOrnithology files, ofecological succession on a man-made Royal Ontario Museum, Toronto. peninsula. M.Sc. Thesis, University of Pria, I.M. and D. V. W«wloh. 1986. Increased Toronto. numbers and productivy ofDouble

ONTARIO BIRDS AUGUST 1988