Trends in fish prey capture by common terns following zebra mussel invasion : do terns track fish species abundance? /

The Common Tern (Sterna hirundo) is a ground nesting colonial seabird. Terns rely primarily on small prey fishes which they obtain through plunge diving for their survival as well as the survival of their offspring during the breeding season. The zebra mussel (Dreissena polymorpha) is a small bivalve mollusk that invaded North American waters in the late 1980's. Through its suspension feeding, the zebra mussel has the ability to alter the entire aquatic ecosystem, ultimately leading to a reduction in pelagic organisms including small prey fish. The objective of the study was to determine what (if any) indirect effects the invasion of the zebra mussel has had on fish prey captured by terns. The study took place in two separate two-year periods, 1990-91 and 1995-96 on a concrete breakwall off the north shore of Lake Erie near Port Colborne, Ontario. Daily nest checks revealed clutch initiation dates, egg-laying chronology, hatching success and morphological egg characteristics (length and breadth). Behavioural observations included time each sex spent in attendance with its brood, the frequency of feeding chicks and the prey species composition and size fed to chicks as well as to females (courtship feeding). Egg sizes did not differ between study periods, nor did feeding rates to chicks, suggesting that food was not a limiting resource. Terns spent less time with their broods (more time foraging) in the 1995-96 period. However, they also had significantly larger broods and fledged more offspring. The time of each individual foraging trip decreased, suggesting that fish were easier to obtain in 1995 and 1996. Lastly, kleptoparasitism rates decreased, suggesting that the costs of foraging (time, energy) actually decreased as fewer birds adopted this strategy to compensate for what I assumed to be a lack of available food (fish). The only significant difference between the periods of 1990, 1991 and 1995, 1996 was a change in diet. Terns delivered significantly fewer rainbow smelt and more emerald shiner in 1995 and 1996. However, the average size of fish delivered did not change. Thus, there was little impact on prey captured by Common Terns in Lake Erie since the invasion of the zebra mussel.

Estimate from the County of Welland to S.D. Woodruff for engineering services in marsh lands drainage for 1 year

Estimate from the County of Welland to S.D. Woodruff for engineering services in marsh lands drainage for 1 year, Dec. 1857.

Engineer services in the marsh lands drainage to the 28th of April inclusive to Frederick Holmes, Louis Clement and Thomas Baird

Engineer services in the marsh lands drainage to the 28th of April inclusive to Frederick Holmes, Louis Clement and Thomas Baird. Signed by S.D. Woodruff, April 28, 1855.

Engineer services in the marsh lands drainage to the 29th day of August inclusive to Frederick Holmes, Thomas Baird and Thomas Gilleland

Engineer services in the marsh lands drainage to the 29th day of August inclusive to Frederick Holmes, Thomas Baird and Thomas Gilleland. Signed by S.D. Woodruff, Aug. 31, 1855.

Engineer services in the marsh lands drainage to the 29th day of August inclusive to Frederick Holmes, Thomas Baird and Thomas Gilleland, signed by S.W. Woodruff

Engineer services in the marsh lands drainage to the 29th day of August inclusive to Frederick Holmes, Thomas Baird and Thomas Gilleland, signed by S.W. Woodruff. This copy contains a note to Fred Holmes from S.D. Woodruff, Sept. 11, 1855.

Engineer services in the marsh lands drainage for the months of December, 1855 and January, February and March of 1856.

Engineer services in the marsh lands drainage for the months of December, 1855 and January, February and March of 1856. Signed by S.D. Woodruff, March 31, 1856.

Engineer services in the marsh lands drainage for the months of December, 1855 and January, February and March of 1856 to Frederick Holmes and Joseph Simpson

Engineer services in the marsh lands drainage for the months of December, 1855 and January, February and March of 1856 to Frederick Holmes and Joseph Simpson. Signed by S.D. Woodruff, April 1, 1856.

Engineer services in marsh lands drainage for the months of April, May and June, 1856 to Fred Holmes, Joseph Simpson and Thomas Baird

Engineer services in marsh lands drainage for the months of April, May and June, 1856 to Fred Holmes, Joseph Simpson and Thomas Baird. Signed by S.D. Woodruff, June 30, 1856.

Engineer services in marsh lands drainage for the months of July, August and September, 1856 to Fred Holmes, Joseph Simpson, Thomas Baird and Rose Osborne

Engineer services in marsh lands drainage for the months of July, August and September, 1856 to Fred Holmes, Joseph Simpson, Thomas Baird and Rose Osborne. This is signed by S.D. Woodruff, Oct. 1, 1856.

Engineering services in marsh lands drainage for the months of October, November and December

Engineering services in marsh lands drainage for the months of October, November and December. This is signed by S.D. Woodruff, Dec. 31, 1856.

Engineering services in marsh lands drainage for the months of January, February, March and April for Fred Holmes, Joseph Simpson, D. Davidson, Rose Osborne, Henry Wilson and William Baird

Engineering services in marsh lands drainage for the months of January, February, March and April for Fred Holmes, Joseph Simpson, D. Davidson, Rose Osborne, Henry Wilson and William Baird. This is signed by S.D. Woodruff, May 1, 1857.

Engineering services in marsh lands drainage for the months of May, June, July and August 1857 for Fred Holmes, Joseph Simpson and William Baird

Engineering services in marsh lands drainage for the months of May, June, July and August 1857 for Fred Holmes, Joseph Simpson and William Baird. This is signed by S.D. Woodruff, Aug. 31, 1857.