Nesting ecology of an ice-associated seabird, Kittlitz's murrelet, at the northern edge of its range

One approach to improving predictions about a species’ response to projected environmental changes is to compare populations in current environments that represent expected future conditions. However, we often know more about a species at the core of its range, where numbers usually are greatest, which can skew inference. We studied the Kittlitz's murrelet (Brachyramphus brevirostris), an ice-associated seabird of conservation concern, at the northern edge of its breeding range in northwestern Alaska, USA, 2022–2023. Unlike most seabirds, Kittlitz's murrelets nest solitarily in steep and rocky mountainous terrain and therefore few nest records exist, especially outside of its core breeding range in south-coastal Alaska. We estimated nest density at 2 study sites, telemetered 4 nesting murrelets to identify foraging areas, and explored methods for increasing nest detection. Across the 2-year period, we found 7 nests, including 3 with the aid of a thermal camera. Although we did not find any nests at 1 study site, nest density at the other site was 4.25 nests/km² (95% credible interval = 3.29–5.38). All nests failed, mostly due to predation, which likely was facilitated by our research activities. Three of 4 tags reported at least once within 2 weeks of deployment, and one reported for 3 months. Immediately after tagging, murrelets flew ~50 km southward into turbid waters near river outflows and also to areas at the margin of sea ice extent, which are habitats that closely resemble the glacially-influenced waters in the core of its breeding range. Our results provide insights into Kittlitz's murrelet life history and ecology in the data-poor northern portion of its range that should help balance information with that from the data-rich southern portion of its range and improve predictions about this species’ response to loss of ice habitats.