Age and hunting success in the brown pelican: influences of skill and patch choice on foraging efficiency

Abstract

Age-related differences in the foraging efficiency of piscivorous birds may be the results of differences in foraging skill, patch usage, or both. Brown pelicans were observed while foraging around a small Caribbean island. Areas where the birds fed were subdivided into small, homogeneous subunits (patches), and the bird's foraging success and patch use were noted and analyzed using multivariate techniques. Adult birds were found to be better at capturing prey under all conditions than were juveniles, but the differences were small in some patches. The density of prey and the birds' foraging success influenced the foraging efforts of adult and juvenile pelicans to similar degrees. Both age groups utilized local enhancement in their foraging, but such behavior augmented the foraging success only of juvenile birds. Both age groups often fed in patches where their foraging success was quite low. Such behaviour was much more costly for juvenile than for adult pelicans.

Age-Specific Diving and Foraging Behavior of the Great Grebe(Podicephorus major)

“…We have shown that adult Great Grebes forage more efficiently than juveniles, an age-related feature common in other birds (Orians 1969; Morrison et al 1978;Searcy 1978;Burger 1980;Schnell et al 1983;Brandt 1984;MacLean 1986;Carl 1987;Arnqvist 1992;Papakostas et al 2005). Foraging efficiency is supposed to increase with age and experience (Buckley and Buckley 1974;Morrison et al 1978;Schnell et al 1983;Brandt 1984), and foraging inefficiency of juveniles has been suggested as contributing to their higher early age mortality (Lack 1954;Ashmole 1963;Weimerskirch 2002).…”

“…Foraging efficiency is supposed to increase with age and experience (Buckley and Buckley 1974;Morrison et al 1978;Schnell et al 1983;Brandt 1984), and foraging inefficiency of juveniles has been suggested as contributing to their higher early age mortality (Lack 1954;Ashmole 1963;Weimerskirch 2002). Foraging efficiency could therefore be expected to be under strong selection pressure, which means that individuals able to learn fast have high survival rates (Morrison et al 1978).…”

“…For birds in general, mechanisms to compensate for reduced foraging efficiency include more time searching for and handling prey (Groves 1978;Burger 1980), use of different areas and foraging methods (Brandt 1984;Edwards 1989) or juveniles relying on different prey species or different prey sizes (Wunderle 1991;Papakostas et al 2005). However, regardless of the mechanism used by juveniles to obtain sufficient amounts of food, their increased efforts imply increasing energy expenditure (Buckley and Buckley 1974;Morrison et al 1978).…”

“…fish : Eckert 1987;mammals: Gillis 1998;birds: Weimerskirch 2002). In birds, a common reason for age-related performance is foraging efficiency (Brandt 1984;Marchetti and Price 1989;Wunderle 1991;Forslund and Pärt 1995), which can be due to: a) morphological limitations such as incomplete skeletal, bill, muscle or neurological maturity; b) as yet undeveloped learning which can be developed by observation, previous experience and the need for a prey searching image; c) different nutritional requirements (adults allocate energy and nutrients for moulting and juveniles allocate protein for growth); d) social interactions such as hierarchic access to feeding areas, cleptoparasitism, and predation risk (Orians 1969;Verbeek 1977;Morrison et al 1978;Burger 1980;MacLean 1986;Marchetti and Price 1989 and review in Wunderle 1991). These differences between juveniles and adults appear to be responsible for the delayed breeding in birds in general and seabirds in particular, whose breeding frequently occurs after three-four years and sometimes after ten years (Ashmole 1963;Lack 1966;Weimerskirch 2002).…”

King penguins adjust their diving behaviour with age

“…Parental efficiency is thus expected to increase with age through increased foraging abilities of the parents in the European shag, Phalacrocorax aristotelis, for instance (Daunt et al, 1999). However, evidence of improved foraging ability with age in free-ranging individuals is scarce [but see Brandt (Brandt, 1984) for the brown pelican, Pelecanus occidentalis], and the precise mechanisms by which such improvement may occur remain unclear. These mechanisms may be easier to highlight when individuals are subjected to strong environmental conditions (Daunt et al, 2007;Lescroël et al, 2009).…”