Abstract
Migratory birds often travel long distances between non-breeding and breeding areas. The suitability of weather and foraging conditions they experience upon arrival at their breeding grounds is an essential component explaining the timing and success of reproduction. Climate change has been identified as a major contributor to "mismatches" in resource phenology and timing of reproduction in animal populations. Climate models project a disproportionate degree of warming at high latitudes, thus the potential for marked temperature-related mismatches in polar regions. Timing of breeding for many Arctic species is also governed by snowmelt. Current models project a general increase in winter precipitation for the Arctic, which can lead to years of delayed snowmelt despite the overall warming trend. This delayed snowmelt could affect phenology, or the availability of resources for egg production. We use an unplanned contrast in dates of snowmelt during a two year research program in the Canadian Arctic to explore the hypothesis that, for Arctic-breeding shorebirds with fixed clutch sizes and an income-breeding strategy, adjustment of reproductive effort to delayed snowmelt could result in a reduced egg size. We compared egg volume in clutches of several shorebird species in the two consecutive years. We found significant variation in egg volume between years, with eggs approximately 5% smaller in the year of late snowmelt, suggesting that shorebirds faced with adverse conditions upon arrival to their breeding grounds can respond by decreasing egg-size. A larger sample of years, sites and shorebird species would help to clarify the generality of this response.