High latitude wetlands, particularly ponds, are experiencing drastic changes in their hydrology (i.e. drying and shrinking) due to the recent temperature increases in the Arctic. These changes in pond hydrology may affect the dynamics between the timing of resource availability and arrival of migratory birds that depend on these ponds during their breeding season. Our goal is to assess the relationship between pond size and bird communities in order to provide insights into potential outcomes of altered hydrology due to climate change. The study was conducted in Izembek National Wildlife Refuge, Alaska. We visited 9 sampling sites representing 3 pond size categories (small, medium and large) in 2011. We continued sampling with 12 and 16 sampling sites representing 4 pond size categories (extra small, small, medium and large) in 2012 and 2013, respectively. Bird species presence/absence and abundance data were collected for each pond on a daily basis from late May through late August (full breeding season starting with the arrival of migratory birds). Pond characteristics, including water pH, salinity, conductivity, dissolved oxygen, and temperature were also collected for analysis. We performed ordination and two-way cluster analysis to describe bird communities and calculate correlations between bird abundance and pond characteristics.
Results/Conclusions:
Larger ponds supported higher bird species diversity, likely due to their diverse habitat availability. Ordination analysis revealed that pond area was the most important variable correlated with bird communities visiting Izembek ponds. Four measures of pond temperature (minimum and maximum temperatures in May and June) also showed strong relationships with bird communities as a product of pond area due to thawing cycles of different pond size categories. We also demonstrated correlations between bird species and pond size, including positive associations of golden-crowned sparrow with larger ponds, and least sandpiper with smaller ponds. Cluster analysis indicated that dabbling duck species have a preference for larger ponds. Sandpiper species visit all pond size categories, but are mostly abundant in smaller ponds. According to our results, the scenario of a ‘larger pond dominated Arctic’ due to warming may diminish habitat availability for sandpipers and negatively affect these birds during their breeding season. Under the assumption of a ‘smaller pond dominated Arctic’, dabbling ducks may lose their preferred habitat type and resources. These results help us to understand pond area-bird occupancy relations in Arctic wetlands, and the potential effects of climate change on migratory bird species relying on resources of high-latitude communities.