Search

Start Over Creator Lekuona, Jesús M.

1. Food intake, feeding behaviour and stock losses of cormorants, Phalacrocorax carbo, and grey herons, Ardea cinerea, at a fish farm in Arcachon Bay (Southwest France) during breeding and non-breeding season

Creator:
Lekuona, Jesús M.
Type:
article and TEXT
Subject:
aquaculture, diet, foraging parameters, impact, and piscivorous birds
Language:
English
Description:
The feeding ecology of cormorants and grey herons were investigated at a fish farm in Arcachon Bay (southwest France) during both breeding and non-breeding season. Cormorants were mainly recorded during winter and grey herons during both breeding and wintering seasons. Adult cormorants and herons were the most abundant age clas at the fish farm. Adult cormorants and herons were more successful at feeding than first-years and although younger birds spent more time feeding and their biomass intake rates remained lower than those of adults birds. Cormorants and herons took the same biomass intake per feeding session at the fish farm during the non-breeding season, about 200 g. The impact of the two ichthyophagous birds (cormorant and grey heron) was estimated as 53.0% (average predation of cormorant per year) and 10.8% (mean predation of heron per year) of the annual yield of the fish farm. This imposed a significant economic loss due to low productivity of the farm.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/

2. Kleptoparasitism in wintering grey heron Ardea cinerea

Creator:
Lekuona, Jesús M.
Type:
article and TEXT
Subject:
age, feeding parameters, handling time, and robbery attemps
Language:
English
Description:
Eighty-six cases of kleptoparasitism in grey herons, most of which were intraspecific, were observed in northern Spain and southwest France during four winters (1992-1995). Herons more often attacked individually than in groups, but the success was similar in both cases. Robbing success was significantly higher when herons attacked a young bird (44.4%) compared to adults (17.6%). Adult herons were significantly more successful (37.5%) than young herons (10.0%). Handling time had a great effect on the size of the prey item robbed by the herons. Adult herons were more frequently attacked by both young and adult birds. Age- related differences in winter foraging parameters (total time foraging, feeding success and biomass intake) may favour discrimination between victim age classes by kleptoparasites. Adult heron ingested 0.82 g min-1 during the winter season and young heron 0.45 g min-1. For kleptoparasites adult herons seems to be a more profitable species than young. Kleptoparasitism increased the biomass intake of the pirate (62.8 g more than the normal intake of a young heron), probably to compensate for the inefficiency of young birds.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/