Components of productivity in black-legged kittiwakes, Rissa tridactyla: response to supplemental feeding

• Main Authors: Verena A. Gill, Scott A. Hatch
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2002
• Subjects: rissa tridactyla; Alaska
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.595.5676; http://alaska.usgs.gov/science/biology/seabirds_foragefish/products/publications/Gill_and_Hatch_2002_Components_productivity_BLKI_response_to_supplemental_food_JAB.pdf

In contrast to the high productivity of black-legged kittiwakes in Britain, kittiwakes at many colonies in Alaska have failed chronically to reproduce since the mid 1970s. To determine if food is limiting productivity and, if so, at what stages of nesting food shortages are most severe, in 1996 and 1997 we supplementally fed kittiwakes nesting on an abandoned building. The effects of feeding were stronger in 1997 than in 1996, possibly because naturally occurring prey were of poorer quality in 1997. Consump-tion of supplemental herring declined as egg laying approached then increased slowly during incubation and more rapidly after hatching. All of the six components of productivity we studied were improved by supplemental feeding to some degree. Supplemental food did not significantly alter laying success in either year, although fed pairs bred at slightly higher rates than unfed pairs in 1997, the poorer food year. In 1996 and 1997, extra food noticeably increased clutch size and hatching success, but significantly so only in 1997. Fledging success and productivity were substantially augmented by feeding in both years. Fed pairs fledged twice as many chicks per nest as did unfed pairs in 1996 and three times as many in 1997. Fed and unfed pairs lost