Effects of feeding height and distance from protective cover on the foraging behavior of wintering birds

Foraging behavior that balances feeding efficiency with predation risk avoidance may be selected for; thus, foraging animals may choose among sites and achieve various giving-up densities under different feeding conditions. We compared the frequency and duration of visits and the feeding efficiency of a mixed-species wintering bird flock among feeders set up at three heights within woods, at the edge between woods and dense shrub, and in open fields to investigate the feeding height preference of birds and its relationship to the extent of openness of the sites. Carolina chickadees (Parus carolinensis Audubon, 1834) and tufted titmice (Parus bicolor L., 1766) accounted for 96% of the total number of visits to feeders and 95.9% of the total time spent on feeders. Birds tended to visit higher feeders and feeders in the woods and at edge sites more frequently than they visited lower feeders and feeders in open fields. Birds also spent more time on higher feeders and feeders in the woods and at edge sites than on lower feeders and feeders in open fields. However, the feeding height preference changed over the course of observations, and different patterns were observed at different sites. In the woods and at the edge, bird visits shifted to the lower feeders earlier; in contrast, birds preferred higher feeders throughout the period of observation in open fields. Feeding efficiency was lower at open sites than in woods and at edge sites, but birds spent the least time per seed on low feeders at open sites. Seeds on higher feeders and in woods or at edge sites were removed faster. Regardless of the height and locality of feeders, birds preferred energy-rich oil-type seeds over energy-poor striped seeds.

New species of haemoproteids from the avian families Paridae and Sittidae

A unique discoid haemoproteid from the tufted titmouse, Parus bicolor L., is described as Haemoproteus parus. A halteridial haemoproteid from the white-breasted nuthatch, Sitta carolinensis Latham is described as Haemoproteus sittae.

Molecular Genetic Divergence between Avian Sibling Species: King and Clapper Rails, Long-Billed and Short-Billed Dowitchers, Boat-Tailed and Great-Tailed Grackles, and Tufted and Black-Crested Titmice

Surveys of electrophoretic variation in proteins, and restriction site variation in mitochondrial DNA (mtDNA), were conducted to assess the resolving power of these molecular genetic techniques to distinguish four pairs of avian sibling taxa. Samples of rails (Rallus elegans and R. longirostris), dowitchers (Limnodromus scolopaceus and L. griseus), grackles (Quiscalus major and Q. mexicanus), and titmice (Parus bicolor bicolor and P. b. atricristatus) were assayed for allozymes encoded by 34-37 nuclear loci, and for an average of 77 mtDNA restriction sites per individual by 19 endonucleases. MtDNA's of the two rail species showed large-scale size polymorphism and individual heteroplasmy, the first such findings of these molecular features in an avian species. Genetic distances based on allozyme comparisons were small for all assayed taxa (Nei's D ≤ 0.063). The mtDNA assays offered consistently greater resolving power, providing at least five fixed restriction site differences for samples of any taxon pair. The Long-billed and Short-billed dowitchers were especially divergent, differing by at least 24 assayed mtDNA restriction sites and an estimated nucleotide sequence divergence of p = 0.082. We compared these results to previous reports of genetic distances within and among closely related bird species. The mtDNA divergence among dowitchers is near the high end of the scale of such estimates for avian congeners. The mtDNA distances between the pairs of rails (p = 0.006), titmice (p = 0.004), and grackles (p = 0.016) were typical for extremely closely related species, and overlap maximum values reported for some avian conspecifics.

Communication with Shared Song Themes in Tufted Titmice

Individual Tufted Titmice (Parus bicolor) sing 8-12 song themes. Most or all themes in an individual's repertoire are shared with neighbors, although slight but consistent differences often separate neighbors' performances of a particular theme. Birds first begin to sing recognizable themes while still juveniles on their parents' territory. Established territorial residents can modify their themes slightly from year to year to achieve a closer similarity to neighbors' themes. Neighbors matched themes during concurrent singing more often than would be expected at random. Furthermore, titmouse tended to begin singing in response to a neighbor, particularly if it could match the theme. Playbacks of recorded song also evoked matched singing in response. Playbacks of strangers' songs, recorded 3 km away, evoked a less intense response than did playbacks of neighbor's songs, but an attempt to demonstrate individual recognition of a neighbor's shared themes failed. Evidently, the advantages of coordinated singing by opponents with shared themes outweigh any advantages of individual recognition of neighbors with distinctive songs.