Distributional patterns of a marine bird and its prey: habitat selection based on prey and conspecific behaviour

Abstract

We examined distributional patterns of a pursuit-diving seabird, the common murre Uria aalge, and its fish prey, capelin Mallotus villosus, within the avian foraging range of the largest murre colony in eastern North America: Funk Island, Newfoundland. During chick-rearing, the foraging habitat was previously partitioned into: (1) a high-quality area, 45 km from the colony where energyrich capelin schools were found, which were spatially and temporally persistent and (2) a low-quality area, 60 km from the colony where schools were composed of lower-energy capelin that were ephemeral. At the scale of the foraging range (meso-scale: 1 to 100 km), murres were highly clustered into 25% of the surveyed area, with fewer murres in the low-quality relative to the high-quality area. There were tighter associations among murre and capelin aggregations in the low-quality (1.2 ± 0.2 km) relative to the high-quality area (2.6 ± 0.4 km). This likely resulted from the divergent capelin behaviour and, thus, different foraging strategies used by murres to search for (e.g. memory vs local enhancement) and capture prey. At fine spatial scales (250 m 2 ) within foraging areas, murres were found at lower densities (mode: 2 murres), revealing that interference competition among individuals may be important during prey capture. Modeling revealed that at > 50 murres per 250 m 2 in the highquality area, a murre would have a > 90% chance of increasing its foraging efficiency by switching to forage in the low-quality area. Overall, this scale-dependent aggregative behaviour of murres suggests that cooperative foraging among conspecifics may be important in locating prey at the scale of a foraging range, or murres may simply aggregate in areas of high prey abundance, but competitive interactions among conspecifics become important at the scale of prey capture.

Top marine predators track Lagrangian coherent structures

“…Foraging behavior of seabirds is complex and results from a number of behavioral parameters, such as sight, smell (37,38), memory effect (39), and environmental parameters [chlorophyll concentration (10) or wind speed and direction]. Nevitt et al (40) suggest that seabirds use olfaction to track high concentrations of odor compounds, such as dimethyl sulfide (DMS), and sight when they locate prey patches.…”

Active acoustic examination of the diving behavior of murres foraging on patchy prey

“…The large variety of prey that murres consumed during the study and their ability to switch between one diet for themselves and another for their chicks suggests that to accomplish this, a wide variety of prey types must be quantified, in contrast to most previous seabird− prey studies which have focused on a single prey group (e.g. fish or krill; sensu Ainley et al 1993, Veit et al 1993, Zamon et al 1996, Swartzman & Hunt 2000, Davoren et al 2003, Grünbaum & Veit 2003, but see Kokubun et al 2008). The diving capabilities of foraging murres indicate that the vertical overlap of murres and their prey must also be considered.…”

Mortality of Migratory Birds from Marine Commercial Fisheries and Offshore Oil and Gas Production in Canada

“…Catches vary considerably from year to year within the same region, and even among fishers within a region. In the Atlantic, schools of capelin (Mallotus villosus), an important prey species of both murres and cod, are patchily distributed, leading to clustering of murres in areas of high capelin density (Davoren et al 2003, Davoren 2007. Such areas may be targeted by fishers fishing for cod, which could increase the likelihood of many murres being captured at once in relatively few gillnets Nettleship 1987, Robertson et al 2004).…”