Conservation ecology of salt marsh birds in New England

Salt marshes in New England, USA, have been filled, drained, and degraded since European settlement to increase forage for livestock, reduce insect populations, and expand coastal development. In some New England states, more than 50% of salt marshes have been filled and 90% have been ditched since the early 1900's. The remaining salt marshes are threatened with invasive plant species, coastal development, and sea-level rise. To date, birds dependent on salt marshes have not been systematically surveyed, leaving distribution and abundance information unknown. I coordinated a survey of 235 salt marshes in New England from Maine to Connecticut. I found greater avian species richness on larger salt marshes and marshes close to other marshes, than on small, isolated marshes. Within patch vegetation only influenced avian species richness in Long Island Sound where marshes were smaller and had more invasive plant species cover than in the Gulf of Maine. Landscape context mediated whether patch scale variables were important components in maintaining avian species richness. At the species level, I found concordance between morphological and molecular markers in the hybridization analysis of sharp-tailed sparrows. Hybrids were more closely related to Saltmarsh Sparrows than to Nelson's Sparrows. Flood tides following a new moon synchronized female availability. Saltmarsh Sparrow females initiated nesting immediately after a flood and had 40% greater nest survival rates than Nelson's Sparrows. This, coupled with the scramble-competition polygyny mating strategy of Saltmarsh Sparrow males, partially explains why hybrids are more closely related to Saltmarsh than Nelson's sparrows. Finally, 2 hypothetical sea-level rise scenarios reduced the amount of salt marsh habitat and fragmented the landscape. Patches were smaller, more isolated, and the number of patches increased following sea-level rise. The remaining salt marsh distribution increased the probability of extinction for Seaside Sparrows in Connecticut. Present land conservation practices may become obsolete with the rapidly changing climate as habitats shift on the landscape. Therefore, conservation planners must attempt to anticipate future habitat distributions.