Changes in Isotopic Niches across Stages of the Annual Cycle in the Arctic Tern (<i>Sterna paradisaea</i>)

Abstract

Arctic Terns (Sterna paradisaea) are iconic seabirds of polar latitudes, whose successful reproduction is thought to depend on local food supplies near breeding colonies. We used stable isotopes of carbon and nitrogen in eggs, blood, and feathers of terns breeding in the Canadian High Arctic to compare their isotopic niche between life history stages and between two years. The isotopic niche of terns was smaller during incubation than during pre-breeding or winter. Over two breeding seasons, isotopic profiles of Arctic Terns suggested the high importance of local, exogenous nutrient supplies to form eggs (i.e., an income breeding strategy). Our results illustrate that using stable isotopes to assess the niche of a seabird population during critical periods of its annual cycle could be an essential tool in determining the influence that local forage conditions have on breeding decisions, especially for species that mostly rely on exogenous sources of nutrients and energy for egg production.

Changes in organ size and nutrient reserves of arctic terns (Sterna paradisaea) breeding near a High Arctic polynya

“…At this site, terns rely heavily on zooplankton (e.g., Gammarus setosus, Calanus hyperboreus, Gamaracanthus spp. ; Figure 3) that are typically energy and/or lipid rich (Percy and Fife 1981;Scott et al 2000) and abundant in the polynya less than 1 km away (Clayden et al 2015;Pratte et al 2018;Mallory pers. obs.…”

“…In females, we suspect that some of these endogenous protein resources were used for egg formation (see also Hatch 2002), although the majority of resources would have come from local exogenous foods because terns are income breeders (relying on resources from the local environment rather than stored internally; Hobson, Sirois, and Gloutney 2000;Pratte et al 2018). The main driver of the decrease in gizzard size might be the relative disuse of this organ during egg laying (females) and incubation (both) compared to heavy use during the energetically expensive, northward migration (Raveling 1979;Jacobs et al 2011;Mathot et al 2019); this could also be affected by a shift in diet during these periods (Pratte et al 2018;Mallory et al 2019). Unlike observed declines in gizzard size, male and female terns showed no consistent change in the size of other organs, suggesting that these other organs are not as plastic through the breeding season.…”

“…Carcasses were labeled with a unique identifier tag on the leg and then placed individually in small plastic bags and placed in a −20°C freezer within 2 hours of collection. These specimens were collected to answer a variety of research questions on wildlife health (e.g., diet, parasites, and contaminants; Provencher et al 2014;Pratte et al 2018;Mallory et al 2019).…”

Differences in tail feather growth rate in storm-petrels breeding in the Northern and Southern hemisphere: a ptilochronological approach

“…in successful compared to failed breeders (Crossin et al, 2013). Increased reproductive costs negatively affected the breeding success in the following year, and birds may even forego breeding if the costs are too high (Crossin et al, 2013; Minguez, 1998; Pratte et al, 2018).…”

Peer Review #1 of "Differences in tail feather growth rate in storm-petrels breeding in the Northern and Southern hemisphere: a ptilochronological approach (v0.2)"

“…in successful compared to failed breeders (Crossin, Phillips, Lattin, Romero & Williams, 2013). Increased reproductive costs negatively affected the breeding success in the following year, and birds may even forego breeding if the costs are too high (Crossin et al, 2013;Minguez, 1998;Pratte, Boadway, Diamond, & Mallory, 2018).…”