04/07/2004 Council Packet - Laserfiche WebLink

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• • • We added a new aspect to the colony monitoring this season by employing a tree climber to assess nesting activity from tree top level. The climber and field team first visited the colony on May 29, 2003. The climber went to the top of five trees and was able to directly observe a total of 55 nests, including three Great Egret nests. He noted birds active in 32 of the 55 nests he observed, for an occupancy rate of 58 %. Two of the three egret nests contained eggs, the third had an adult in incubating posture. Many of the heron nests had chicks that were noticeably different in size from nest to nest indicating a range of ages. Colony monitoring indicated much activity by the birds during the month of June. This is in stark contrast to 2002 when then site had been abandoned by June 4, 2002. Glenn Fuchs reported, " On Sunday 29 June and again on Wednesday 2 July, Art H. and I conducted simultaneous observations of the activity on the island concentrating on flights to and from the island. On both days were observed flights averaging about one flight per minute over the course of a one hour time period." On June 20th, 2003, Steve Kittelson conducted a field visit to 15 trees and made observations of bird activity from below the trees. In these trees he observed 40 nests, 20 of which were occupied by Great Blue Herons with 33 live young and 4 dead young. He also observed three active Great Egret nests with 5 young. The remaining 16 nests were seemingly empty, although some occurred in trees below which there were eggshells or whitewash indicating hatching or the presence of young earlier in the season. The question then becomes, were young hiding in the nests and unobservable or had they already fledged (grown sufficiently to have flow away) or walked away from these nests as he approached? We do not know the answers, but June 20th seems just too early for successful fledging. Also, on June 20th, the resident pair of eagles was present over the colony and Steve noted one eagle young in the nest during his visit. None of the observers who watched the colony during the season ever reported any negative interactions between the eagles and herons or egrets. An aerial survey on July 1st indicated 100 —150 active heron nests and 3 -5 broods of Great Egrets present on the island. Empty nests were also noticeable from the air. The field team, including the climber, also visited portions the colony on July 3rd and the 10th. The field visit on the 3rd revealed that some portions of the colony were no longer active and nests were empty of young or adults. However, 20 young herons at the stage of short flights or "branching " were observed in one area east of the eagle nest. On July 10th, the climber and crew returned to the colony and checked nests that could be seen by the climber from the top of 4 trees. All 37 nests that the climber could see into from his tree top position were empty of live birds except one with one young Great Blue Heron. Eleven of the nests had at least one visible carcass. The field crew noted the presence of 18 herons flying, both adults and young of the year. It appeared as if most