Foraging closer to the colony leads to faster growth in little auks

Abstract

Knowledge of foraging behaviour is essential to understand both the ecological roles of seabirds and the constraints acting upon them in marine ecosystems. Here, we investigated foraging trips of a small planktivorous alcid, the little auk Alle alle, using miniature GPS loggers. We performed the study in 2 large breeding colonies in west Spitsbergen (Hornsund and Magdalenefjorden) with contrasting oceanographic conditions (Arctic and Atlantic environments, respectively). Generally, in both locations little auks foraged in areas with low sea surface temperature (Arctic-type water, marginal ice zone, and frontal zones) where preferred zooplankton are commonly abundant. In the Arctic environment (Hornsund), birds foraged significantly closer to the colony (up to 60 km) compared to up to 150 km in the Atlantic environment (Magdalenefjorden). Hatching and breeding success and chick survival up to 20 d as well as chick body mass parameters were similar in both studied colonies. However, chicks in the Arctic environment (Hornsund) achieved both peak body mass and fledging age earlier, suggesting faster chick growth than in the Atlantic environment (Magdalenefjorden). The importance for breeding little auks of nearby cold water foraging grounds may make them sensitive to predicted climate change with serious negative consequences for body condition, future survival and breeding success.

Large versus small zooplankton in relation to temperature in the Arctic shelf region

“…This was also the basis for our assumption that in examining the larger Calanus fraction obtained from LOPC measurements we were mainly determining the older life stages of C. glacialis in the Arctic Zone and of C. finmarchicus in the Atlantic Zone. The net zooplankton catches described by Jakubas et al (2013) in the same area (Arctic-type waters, the Hornsund area) and at the same period as our study (the end of July) showed that C. glacialis represented 70% of the older life stages (CIV, CV and adults) of both mentioned Calanus species and that the fifth copepodite of C. glacialis constituted half of this amount. Moreover, multiyear observations conducted by Kwasniewski et al (2012) showed the substantial domination of C. glacialis older copepodite stages over C. finmarchicus in the Arctic shelf community at this time of the year.…”

“…We decided to broaden the size range for Calanus spp. suggested by Basedow et al (2010) to the upper limit applied by Jakubas et al (2013), who combined net sampling together with LOPC measurements taken together at the same time in the research area. The Calanus size fraction classified as the size range of 1-2.5 mm according to Jakubas et al (2013) and Trudnowska et al (2014) was composed of Calanus spp.…”

“…This study provides only high-resolution LOPC measurements -information about zooplankton species composition is based on numerous previous studies conducted in the same study area (e.g., Kwasniewski et al 2010;Kwasniewski et al 2012;Jakubas et al 2013;Stempniewicz et al 2013;Trudnowska et al 2014;Trudnowska et al 2015;Trudnowska et al 2016). Using the abundance estimates and size structure data derived from the LOPC, we grouped plankton into two size fractions: a small size fraction (0.25-1.0 mm ESD), consisting of, e.g., Calanus nauplii, Oithona spp., Microcalanus spp., Pseudocalanus spp., and a large size fraction (1.0-2.5 mm ESD) -hereafter Calanus -represented predominantly by the older life stages (CIV, CV, adult) of Calanus spp.…”

Factors affecting leucocyte profiles in the little auk, a small Arctic seabird

“…In contrast, the thin-billed prion chicks, showing an increase in the relative number of heterophils and the H/L ratios with age, experienced poor feeding conditions (Quillfeldt et al 2008). The study area (Magdalenefjorden) is generally considered a suboptimal feeding ground, with a prevalence of warmer water masses that affect the birds' foraging behaviour and chick growth (Kwasniewski et al 2010;Jakubas et al 2011Jakubas et al , 2013. A study comparing body mass and the H/L ratio in little auk chicks between the colony investigated in the present study and in Hornsund (SW Spitsbergen) showed no differences in those variables in a year when the food supplied was of similar quantity and quality .…”

“…However, after the realimentation period from 22 to 42 days of life, there were no significant differences in leucocyte profiles and body mass between food-restricted and ad libitum chickens. Little auk parents are capable of intensifying their parental efforts under suboptimal food conditions (Harding et al 2009;Jakubas et al , 2011Jakubas et al , 2013Kwasniewski et al 2010) and can increase their provisioning effort. It is hypothesised that such a reaction is triggered by the increased begging behaviour in chicks with an elevated corticosterone level (Kitaysky et al 2003), which is related to the H/L ratio (Davis et al 2008).…”