Birds of the Week # 33
The American Robin (Turdus migratorius) is a migratory songbird of the true thrush genus and Turdidae, the wider thrush family.This bird breeds throughout most of North America, from Alaska and Canada southward to northern Florida and Mexico. While robins occasionally overwinter in the northern part of the United States and southern Canada, most migrate to winter south of Canada from Florida and the Gulf Coast to central Mexico, as well as along the Pacific Coast. Most depart south by the end of August and begin to return north in February and March (exact dates vary with latitude and climate). The distance by which robins migrate varies significantly depending on their initial habitat; a study found that individual robins tagged in Alaska are known to travel as much as 3.5x further across seasons than robins tagged in Massachusetts.
The Brown-headed Nuthatch (Sitta pusilla) is a small songbird found endemic to pine forests throughout the Southeastern United States. Genetic analyses indicated low differentiation between northern and southern populations in Florida, but the study also found lower genetic diversity among south Florida populations that may be a result of the increased habitat fragmentation that was documented. The Bahama nuthatch was formerly considered a subspecies (S. p. insularis), has since been reclassified as its own separate species. Two recent studies assessing vocalizations in Bahama and continental nuthatch populations found important differences. One of the studies also demonstrated that continental and Bahama populations did not respond aggressively to calls of the other population. This type of call-response study is often used to help define cryptic species. The bird, like other nuthatches, possesses a sharp black nail-like beak, which it uses to pound open seeds. It is a frequent visitor to feeding stations and is highly fond of sunflower seeds and suet cakes. Bold and inquisitive, this bird is readily approachable by humans. The bird is regularly observed using a small chips of bark, small twigs, and pine needles held in its beak as tools to dig for insects. The nuthatch exhibits other curious behaviors such a cooperative groups where groups of 3-5 adults provide care at a single nest. Recent genetic assessments suggest some of the putatively non-breeding adults associated with these groups may actually breed with individuals in neighboring territories. This nuthatch also exhibits a wide range of other social behaviors that include social grooming and male-female duets similar to those observed for the Pygmy Nuthatch.
© HJ Ruiz – Avian101