Monday, August 2, 2010: 3:20 PM
334, David L Lawrence Convention Center
Background/Question/Methods Over the next few decades, climate change will likely have significant impacts on shorebirds along the Atlantic Coast. In particular, climate-related sea-level rise may reduce nesting habitat availability, inundate favored roosting and foraging sites, and cause direct mortality of eggs and chicks due to flooding. In June 2009, as part of an ongoing study at Onslow Beach, North Carolina, we were able to quantify the behavioral and demographic responses of Wilson’s plovers (Charadrius wilsonia) to a natural experiment of the effects of sea-level rise due to an Atlantic Coast sea-level anomaly.
Results/Conclusions In 2008-2009, we studied 45 Wilson’s plover nests (20 in 2008, 25 in 2009). We observed adults and their broods moving 0.03–1.82 km from their nest sites to their final foraging territories. Habitats crossed by birds during this movement included vegetated sand flats, dunes, ocean beach, ephemeral pools, and intertidal zone. In 2008, the final foraging territory was always a fiddler crab (Uca spp.) mudflat; however, in 2009, 5 of 11 broods established final foraging territories in more than one habitat. The use of a second habitat type in addition to fiddler crab mudflat by broods in 2009 occurred during an Atlantic Coast sea-level anomaly which inundated most of the available fiddler crab mudflats in our study area, regardless of tidal stage, from 18-27 June 2009. According to NOAA, sea-level heights averaged >0.2 m higher than predicted levels from North Carolina to New Jersey in June 2009. We compared the proportion of broods using fiddler flats and foraging behaviors of broods pre-, during, and post-sea-level anomaly (SLA) in 2009 to similar time periods in 2008. Wilson’s plover broods used fiddler flats less during the SLA in 2009 than during the same time period in 2008 (2008 = 0.44 ± 0.16, 2009 = 0.17 ± 0.08 proportion of brood observations on fiddler mudflats). We also observed a decline in rates of fiddler crab-specific foraging behaviors, and an increase in pecking for insects, between 2008 and 2009. We found similar fledging success between years (2008 = 0.88 ± 0.26, 2009 = 1.00 ± 0.25 fledglings/breeding pair). We also estimated in-season chick survival using a Cormack-Jolly-Seber model; we found no effect of year on chick survival. Wilson’s plovers in our study exhibited plasticity in habitat use and foraging behaviors when this preferred habitat was inundated due to a sea-level anomaly with no observed decrease in fledging success or chick survival.
Results/Conclusions In 2008-2009, we studied 45 Wilson’s plover nests (20 in 2008, 25 in 2009). We observed adults and their broods moving 0.03–1.82 km from their nest sites to their final foraging territories. Habitats crossed by birds during this movement included vegetated sand flats, dunes, ocean beach, ephemeral pools, and intertidal zone. In 2008, the final foraging territory was always a fiddler crab (Uca spp.) mudflat; however, in 2009, 5 of 11 broods established final foraging territories in more than one habitat. The use of a second habitat type in addition to fiddler crab mudflat by broods in 2009 occurred during an Atlantic Coast sea-level anomaly which inundated most of the available fiddler crab mudflats in our study area, regardless of tidal stage, from 18-27 June 2009. According to NOAA, sea-level heights averaged >0.2 m higher than predicted levels from North Carolina to New Jersey in June 2009. We compared the proportion of broods using fiddler flats and foraging behaviors of broods pre-, during, and post-sea-level anomaly (SLA) in 2009 to similar time periods in 2008. Wilson’s plover broods used fiddler flats less during the SLA in 2009 than during the same time period in 2008 (2008 = 0.44 ± 0.16, 2009 = 0.17 ± 0.08 proportion of brood observations on fiddler mudflats). We also observed a decline in rates of fiddler crab-specific foraging behaviors, and an increase in pecking for insects, between 2008 and 2009. We found similar fledging success between years (2008 = 0.88 ± 0.26, 2009 = 1.00 ± 0.25 fledglings/breeding pair). We also estimated in-season chick survival using a Cormack-Jolly-Seber model; we found no effect of year on chick survival. Wilson’s plovers in our study exhibited plasticity in habitat use and foraging behaviors when this preferred habitat was inundated due to a sea-level anomaly with no observed decrease in fledging success or chick survival.
