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Food Provisioning by White‐Tailed Tropicbirds: Effects on the Developmental Pattern of Chicks
Author(s) -
Schaffner Fred Charles
Publication year - 1990
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1940275
Subject(s) - foraging , provisioning , biology , payload (computing) , food delivery , ecology , limit (mathematics) , zoology , demography , mathematics , computer science , business , telecommunications , marketing , computer network , mathematical analysis , sociology , network packet
Food provisioning of White—tailed Tropicbird (Phaethon lepturus) chicks by their individually identified parents was studied at Cayo Luis Pena, Puerto Rico, in 1985—1986. This paper describes the pattern of this provisioning from the perspectives of both the chick receiving the food, and the individual parents delivering the food. The interval between feedings delivered by an individual adult was more variable than food payload mass (higher coefficients of variation), and there was no day—to—day relationship between the feeding interval and feed mass. Moreover, adults demonstrated the ability to lift and transport food payloads substantially larger than the mean feed mass. Energetic considerations suggest that there is strong selection for parents to decrease the feeding frequency and increase feed mass, to some limit imposed by either the limits of the parents' delivery capabilities, or the limits of the chick's food receiving (swallowing) capabilities (the volume a chick can ingest in one feeding bout). In fact, the limits of the chick's swallowing capabilities occur well before the parents' delivery limits are reached, and thereby set the feed mass at a weight and volume that is easily within the adults' lifting and transporting capabilities. The mean feed mass is viewed as reflecting a particular “target” payload mass that parents strive to collect as quickly as conditions, and their own individual foraging abilities, will allow, and is a practical compromise between the short—term interests of the chick and those of the adult. While parents are able to collect an abundance of food for their single chick, their pelagic foraging creates an intermittent, or “feast or famine” feeding situation for the chick which promotes the characteristic developmental pattern of slow growth and large fat accumulations. The developmental pattern of White—tailed Tropicbirds and other pelagic birds may be better understood by examining the temporal pattern of feeding, and thus there is a need for more comparative and experimental ecological and physiological studies focusing on patterns of food delivery and their possible effects, as well as the average rate of energy flow.