White-breasted Nuthatch Sitta Carolinensis Research Articles

Phylogeny of Titmice (Paridae): I. Estimate of Relationships among Subgenera Based on DNA-DNA Hybridization

The phylogenetic relationships of titmice and chickadees (Passeriformes: Paridae) were estimated by DNA-DNA hybridization. Fifteen species of parids (representing all six subgenera) and two outgroups, Penduline Tit Remiz pendulinus and Whitebreasted Nuthatch Sitta carolinensis, were radiolabeled and compared pairwise to produce a complete reciprocal set of distance measures. The resulting phylogeny supported the traditional allocation of species to subgenera, except that Parus wollweberi clustered with the North American crested tits (subgenus Baeolophus) rather than the Old World crested tits (Lophophanes). The interrelationships of most subgenera remained unresolved. Nevertheless, a major subdivision in the family was strongly indicated: i.e., the great tits (subgenus Parus) and the blue tits (subgenus Cyanistes) formed a clade that is the sister taxon of the rest of the family. This bifurcation has important ecological, physiological, and morphological ramifications, as it correlates exactly with seed-caching and flocking habits, hippocampal development, and leg-muscle character distributions. These DNA-hybridization results corroborate or complement the phylogenetic relationships among parids supported by other molecular data sets (viz., allozyme, restriction site, and preliminary DNA hybridization analyses).

Supplementary Food Improves the Nutritional Condition of Wintering Woodland Birds: Evidence from Ptilochronology

Using the daily growth of induced feathers as an index, we found that supplementary food significantly improved the nutritional condition of wintering birds of several bark-foraging species, Downy Woodpecker Picoides pubescens, Carolina Chickadee Parus carolinensis, Tufted Titmouse P. bicolor, and White-breasted Nuthatch Sitta carolinensis. In many previous studies of the behavior and ecology of wintering birds, supplementary food on and off site both before and during study periods has remained an uncontrolled variable. We suggest that future work should incorporate knowledge about the accessability of artificial food supplies.

Diurnal Caching Rhythm in Captive White-Breasted Nuthatches Sitta carolinensis

The caching behaviour of mated pairs of White-breasted Nuthatches was studied in a large indoor aviary. Caching intensity, but not feeding intensity, was negatively correlated with time of day. We suggest that storing surplus food early in the day during winter may be important for ensuring adequate food availability during the afternoon when the nuthatches presumably must forage efficiently to deposit sufficient fat reserves before fasting overnight. Moreover, applying a model of the body size of wintering birds as a trade-off between the risks of starvation and predation (Lima 1986), we suggest that caching rather than consuming surplus food as encountered early in the day, and thereby staying thin, may minimize predation risk. Later in the day, nuthatches may have to endure an increased risk of predation as they build fat reserves to reduce the risk of starvation during overnight fasting.