94 Ontario Birds August 2012 Figure 1
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New Niagara Fall s Grea t Egret colony produces late nestlings Bill Watson Introduction Methods In 2011, Great Egrets ( Ardea alb a, hence - The m ain nesting island (#3) is t he forth egrets) nested for the first time at largest of three islands (known locally as a mixed colony of Black-crowned Night- “Weseloh Rocks”) located immediately Herons ( Nycticorax nycticorax , hence - downstream and medially of the large forth night-herons), Double-crested stranded barge on the Canadian side of Cor morants (Phalacrocorax auitu s, hence - Horseshoe Falls, approximately 400 m forth cormorants) and Herring Gulls above the lip of the Falls (Figure 1). I (Larus argentatus ) above Horseshoe Falls made observations from Goat Island on on the Canadian side of Niagara Falls in the New York side of the Falls as well as Ontario. Seasonally, this was a very late from the Canadian shore near the Engi - nesting; young egrets did not fledge un - neerium Building just opposite from the til well into September. In this paper, I barge. I noted the numbers (and nests give details of the discovery of these egret when visible) of night-herons, cor - nestings, compare egg, hatching and morants and egrets. Observations were fledging dates with the currently ac - made from one or both of these loca - cepted dates for these stages in New York tions on 30 June, 29 July, 1, 17 and 26 and Ontario and speculate on the rea - Aug ust and 6 and 9 Sept. I also receiv ed sons for such late nesting. observations from Celeste Morien (CM), Dave Van de Laar (DVL) and Chip We - seloh (CW). 94 Ontario Birds August 2012 Figure 1. Points of observation and nesting islands (Rocks #1, 2 and 3) at Niagara Falls, see text. Results 2011: On 21 April, I counted 172 night- 2010: The main island was visited on 26 herons and 243 cormorants on the main April by helicopter by CW et al. (pers. island, but I saw no Great Egret s. On 1 comm.); they reported 47 cormorant May, CM et al. (pers. comm.) counted nests, 280 night-heron nests and 21 Her - 40 night-herons there from Goat Island ring Gull nests but no Great Egrets or but also did not see any Great Egrets. their nests. On 5 May, from Goat Island On 3 May, CW et al. again visited the I observed at least 140 night-herons and main island island by helicopter and 22 of their nests and 124 cormorants reported 135 cormorant nests, 434 night- and 51 cormorant nests on Rocks # 1, 2 heron nests and 13 Herring Gull nests; and 3 above the Horseshoe Falls (dis - still there were no egrets or their nests. tance and foliage obscured my view of Thus, on 20 May 2011, I was surprised the colony, and these counts represent to find 12 Great Egrets at the colony, only a fraction of the birds and nests in four of which appeared to be sitting on the colony). There were no reports of nests! There were at least 61 night-her ons, any egrets using any of these three is - 168 cormorants and 86 cormorant nests. lands in 2010. Volume 30 Number 2 95 Over the next 10 weeks, I confirmed ing a nestling. With other egrets between that at least two of the egret nests con - the two nesting locations, I observed as tinued to be active on 30 June and 8 July. many as 11 Great Egrets (compared to Viewing from Goat Island on 29 July, only six seen on 1 August). However, I could see as many as seven Great Egrets when I observed the colony from the and, more importantly, three of them Canadian side I was disturbed, because were crouched on a nest and were nearly I could not see any nests where I had full-sized nestlings. observed four nests with a total 12 nest - Returning at mid-day on 1 August, lings on 1 August. The maximum num - to Goat Island, I observed that the three ber of egrets observed on this day from Great Egret nestlings were very active the Canadian side was three adult Great with strong wing flaps combined with Egrets. Perhaps the foliage was too great jumping up and down, but not showing or the egrets had moved more into the in - the ability to hover over their nest. There terior of the woody vegetation. was still some down on their heads. I On 26 August, observing from Goat drove to the Canadian side of the River Island and based on the egrets’ feeding and observed from just north of the En - activity and position of various nests and gineerium Building. I could see an adult nestlings, there appeared to be five egret Great Egret standing over a nest with nests on the islands (four on the main is - what looked like about two inactive land and one on a smaller island to the downy Great Egret nestlings. I also no - west). On 6 September, DVL reported, ticed another Great Egret nest with four “It appears that some of the egrets have medium-sized nestlings. Below this nest left their nests above the Falls and moved was a third Great Egret nest containing to Dufferin Islands” where he spotted three smaller and very inactive downy three egrets “roosting in the trees” (DVL nestlings. Although I realize that obser - pers. comm.) On 7 September, he again vational duplication is possible, I think reported two egrets at Dufferin (because of the numbers of young on Islands and two “in the trees on the each nest and ages of the nestlings) that other island” (colony). I viewed four active Great Egret nests On the morning of 9 September with a total of 12 nestlings. there were no egrets on the island when Three weeks later, on 17 August, I arrived at Goat Island. Within 15 min - there appeared to have been a disrup - utes a single Great Egret appeared at the tion in the colony; the birds were not in largest island where most of the night- their normal positions. I observed four herons and cormorants nested. Two egrets on one nest (based on previous ob - more arrived shortly and there was a servations one of the four was probably flurry of feeding and bill grabbing and an adult with three full size nest ling). pulling activity. The first egret (a par - Through the foliage I observed two ent?) flew from the island and was adults, one of which could be seen feed - quickly pursued by the two (fledglings?) 96 Ontario Birds August 2012 egrets. It appeared that all of the nestling fairly close to the 9 September date, per - Great Egrets had fledged. haps 6 September (+ or – 3 days). The seasonal lateness of this egret 2012: In late March, a Great Egret was nesting, hatching and fledging can be reported near the Niagara Falls colony, put in perspective if we examine the and on 31 March, I counted 23 Great stated phenology dates for Great Egrets Egrets and five occupied nests and wit - in Ontario. LePage et al. (2007) states nessed copulation at the colony. A heli - the early and late nest dates as 20 April copter visit to the island on 25 April and 1 August, respectively. Peck (2007) established that there were about 47 notes that “egg dates in Ontario range Great Egrets present with 17 nests on the from 28 April to 24 June (peck and main island and four more nests on the James 1993a). Incubation periods range next island closer to Canada (CW, pers. from 23 to 27 days, and variable fledg - comm.). On the very early date of 3 ling dates range from 21 to 34 days, with May, an adult Great Egret was observed young leaving and returning to the nest feeding two half-grown nest lings. The fi - to be fed. Young achieve flight ability at nal tally as seen from Goat Island (with seven to eight weeks of age (McCrim - vegetation obstruction) for 3 May was mon et al . 2001).” 25 adults, two nest lings, and thirteen Across the border, New York atlas nests. Obviously, observations are very data from 2000 –2005 provided rev ised limited from afar. early and late egg, nestling, and/or fledg - ling dates for nearly all spe cies. Thus, for Discussion and Conclusions the Great Egret, McGow an and Cor - Although foliage made observations dif - win (2008) have revised egg dates rang - ficult and individual nests were not al - ing from 27 April to 7 July and revised ways directly observed ( i.e. some nest nestling dates of 21 May to 11 August. locations were only inferred when the The incubation period is 25 to 28 days, nestlings were old enough to leave the while the time for young to fly is much nest and approach the adults during feed - longer than reported in the Ontario At - ing), there were probably at least five las at 35 to 42 days (Cadman et al. nests and 13 nestlings. It appears that all 2007). the young Great Egrets fledged between Working backwards, if we assume a 26 August and 9 September 2011. All 13 fledgling date of 6 September and the nestling Great Egrets were observed at mean periods of 25 days for incubation the colony on 26 August and there were and 27.5 days for a nestling period (Le- no indications then that any of them Page et al. 2007), we arrive at very late could yet fly. As there were two fledg - dates of approximately 15 July for egg lings still returning to the colony to be laying and 9 August for egg hatching, fed by an adult on 9 September, the last which are well beyond the late egg date of these nestlings probably had fledged of 24 June (LePage et al.