Flexibility in the bimodal foraging strategy of a high Arctic alcid, the little aukAlle alle

Abstract

A bimodal foraging strategy has previously been described for procellariiform seabird species and is thought to have evolved in response to local resource availability being too low for adult birds to meet chick requirements and simultaneously maintain their own body condition. Here, we examine the dual foraging trip pattern of an alcid, the little auk Alle alle, at five colonies with contrasting oceanographic conditions. In spite of large variation in local conditions, little auks at all colonies showed the same general pattern of alternating a single long‐trip with several consecutive short‐trips. However, we found that the foraging pattern was flexible and could be adjusted at three levels: (1) the length of long‐trips, (2) the frequency of short‐trips, and (3) the total time spent foraging. Birds facing unfavorable conditions increased the duration of long‐trips and reduced the number of short‐trips. These adjustments resulted in reduced provisioning rates of chicks despite the fact that birds also increased the time allocated to foraging. Travel times during foraging trips were positively correlated to the total duration of the trip suggesting that differences in trip length among colonies were partly driven by variation in the distance to foraging areas. Most birds spent substantially more time traveling during long compared to short‐trips, indicating that they accessed distant foraging areas during long‐trips but remained close to the colony during short‐trips. However, the difference in travel times was small at the site with the most favorable conditions suggesting that bimodal foraging in the little auk may be independent of the existence of high‐quality areas at distance from the breeding ground.

Foraging by little auks in the distant marginal sea ice zone during the chick-rearing period

“…Visual inspection of the graphs plotted with a custom-made application working in the MS Excel environment distinguished three main types of little auk activity: presence in the colony, Xight and presence on the water (Tremblay et al 2003;Welcker et al 2009). A sudden and steep increase in temperature (10-15°C above the air temperature) was interpreted as arrival at the colony.…”

“…Such a bimodal foraging strategy has recently been described in the little auk (Alle alle; Steen et al 2007;Welcker et al 2009;Wojczulanis-Jakubas et al 2010). This small planktivorous alcid breeding colonially in the high Arctic is considered to be the most numerous seabird in the Palaearctic.…”

“…Owing to the high cost of foraging (the time and energy expended on feeding combined with the high cost of diving and Xapping Xight; Gabrielsen et al 1991;Konarzewski et al 1993), little auks would be expected to avoid increasing Xight distance and to forage close to the colony. Welcker et al (2009) calculated theoretical maximum foraging ranges of short trips of 12 and 33 km and long trips of 130 and 219 km in two colonies studied on Spitsbergen, based on the mean Xight times of parent birds equipped with miniature time-depth recorders. The range of the short trips corresponds well with the tens of kilometres reported from other colonies (reviewed in Stempniewicz 2001).…”

Variability inCalanusspp. abundance on fine- to mesoscales in an Arctic fjord: implications for little auk feeding

“…Zooplankton was sampled by vertical hauls (c. 0.5 m s (1 ) with hand-pulled specially manufactured WP2 plankton nets (mesh size 0200 mm, sampling area00.25 m 2 ). We restricted our sampling to the upper 25 m of the water column as A. alle rarely dive deeper than 20 m (Falk et al 2000;Welcker et al 2009a;Karnovsky et al 2011). Samples were split in two fractions using a simple box splitter (Motoda 1959).…”

Plasticity in foraging strategies of inshore birds: how Little Penguins maintain body reserves while feeding offspring

“…For instance, if Sooty Shearwaters, Puffinus griseus, seem to respond to a threshold in their body condition below which they will always initiate a long foraging trip (Weimerskirch 1998 other species seem able to alter the length of foraging trips in response to the body condition of the chicks (Weimerskirch et al 2000). Although trips of bimodal durations have been widely reported in procellariiforms , 1997a, Granadeiro et al 1998, Booth et al 2000, Congdon et al 2005), the indication of dual feeding is very limited outside this taxon, with a few alcids as exceptions, such as Thick-billed Murres, Uria lomvia (note that both short and long trips have been reported for that species, but not for the same individuals; Benvenuti et al 1998) and Little Auks, Alle alle (Welcker et al 2009). Aside from Little Auks, all these species are offshore birds, foraging at great distances from their colonies.…”