Sitta Pusilla Research Articles

Helpers liberate female fairy-wrens from constraints on extra-pair mate choice

In cooperatively breeding superb fairy-wrens (Malurus cyaneus), all males contribute to the feeding and defence of young. Despite the expectation that such paternal care should be directed only to relatives, DNA fingerprinting revealed that most offspring (76%, 138 out of 181) were sired by extra-group males that contributed no care, and that almost all broods (95%, 38 out of 40) contained young sired by extra-group fathers. This is the highest known incidence of cuckoldry. This remarkable mating system is produced by female control of fertilization and consistent preference for certain extra-group male genotypes. This choice leads to the production of sons that also gain extra-group fertilizations. One constraint on the extra-pair mate choice of females is the level of parental assistance received from males. Males living in pairs contribute relatively more parental care and are more likely to gain paternity in one of their broods (85%, 11 out of 13) than dominant males in multi-male cooperative groups (30%, 8 out of 27). In groups helpers compensate for the lower parental assistance of dominant males, so the total feeding rate is similar between pairs and groups. This suggests that females allow males in pairs more paternity to ensure their assistance with parental care. Helpers provide an alternative source of paternal investment, and allow females to express unrestricted mate choice. Mating options for females in other species with female control of fertilization may also reflect a trade-off between acquiring the genes of high-quality males for their offspring and parental care of those offspring.

Reciprocal Allopreening in the Brown-Headed Nuthatch

Reciprocal Allopreening in the Brown-Headed Nuthatch

Prealternate Molt in Nuthatches

Nuthatches of the genus Sitta constitute one of the passerine groups in which prealternate (prenuptial) molt is generally believed not to occur. Dwight (1900: 298) discussed this genus with the family Paridae and stated: All the members of this family have only the annual moult. They are peculiar in assuming a juvenal plumage closely resembling the pale nuptial plumage which results from extreme fading of the winter dress. Witherby (in Witherby et al. 1938: 244) remarked that in S. europaea the summer plumage is attained by abrasion rather than by Following Dwight's analysis, Bent (1948) recorded that the prenuptial molt did not occur in S. carolinensis or S. canadensis. Although Norris (1958: 246) found several females of S. pygmaea that were replacing feathers in the nuchal region in March and April, he regarded this as a regrowth of feathers lost in social interactions rather than as prealternate molt; the replacement of contour feathers over nearly every part of the body in early April by one female of that species was considered to be an aberrant instance of prenuptial molt. Norris (op. cit.) stated categorically that There is no prenuptial molt in Sitta pusilla. For most species in the genus, however, I have been unable to find any statement, even a negative one, concerning the occurrence of this On the other hand, there is a partial prealternate molt in the seasonally dimorphic Tichodroma muraria, usually considered a member of the family Sittidae but in a different subfamily. While studying Red-breasted Nuthatches, S. canadensis, for other reasons (Banks 1970), I noticed a spring-taken female that was replacing several ventral feathers. Examination of additional specimens revealed that a partial prealternate molt is of common occurrence in that species. To determine the occurrence, extent, and timing of the molt in the genus Sitta, I subsequently examined most of the seasonally appropriate specimens of nuthatches in the U.S. National Museum of Natural History and the American Museum of Natural History. Through the courtesy of George Watson, I was able to examine specimens from the Yale Peabody Museum that he had collected in the Mediterranean region. Additional specimens were studied at the Musee Royal d'Historie Naturelle in Brussels. A combination of several problems necessarily makes a survey such as this less complete than is desirable (Lanyon 1975). Relatively few persons collect extensively in the months just prior to the onset of breeding, so that population samples are small in the months when prealternate molt might be expected. For some species the material available is too scanty to permit any conclusions to be drawn. Pin feathers are often lost as a specimen is prepared, and if only a few feathers are involved in a partial molt, as seems often to be true in nuthatches, this loss may obscure the occurrence of the Lack of precise information on the time of breeding and of the annual prebasic molt in a species renders it impossible to look specifically for prealternate molt; this situation occurs particularly where there is reason to believe that the onset of breeding is determined by factors other than those that operate in the temperate Palearctic regions. In general, I examined birds taken in the months of February through May for evidence of prealternate This selection of dates proved inadequate for some nuthatch populations of southern Asia and the Philippine Islands, where the nesting season differs from that of nuthatches in temperate areas. Where prealternate molt occurs in a very small proportion of a population, and where it may involve only a few feathers in the molting individuals, it is difficult to distinguish between a true molt and the replacement of feathers fortuitously lost. Some errors of judgement may have resulted from this difficulty, particularly in species represented by small samples. For the reasons mentioned, and various combinations thereof, the fact that I did not find evidence of prealternate molt in certain species or populations of nuthatches should not be taken as a definitive statement that no such molt occurs. It is hoped that the preliminary results reported here will stimulate study by those who have access to appropriate material. The arrangement of the species in the accounts that follow is not meant to be phylogenetic or to imply any concept of relationship. For convenience and because the information is more complete, North American species are listed first. Not all forms in the genus were examined. Species listed by Greenway (1967) but not in this paper are considered to be races of species discussed. Sitta canadensis. -Prealternate molt in the Red-breasted Nuthatch varies from slight (perhaps none in some individuals) to extensive. Most feather replacement occurs on the ventral surface, with the malar

Foraging Relationships of Brown‐Headed Nuthatches and Pine Warblers

Foraging behavior and interactions between Brown—headed Nuthatches (Sitta pusilla) and Pine Warblers (Dendroica pinus) were studied in longleaf pine lands of Louisiana during the fall and winter of 1963—64 and 1964—65. Both species frequently were members of flocks that formed around Carolina Chickadees (Parus carolinensis) and Tufted Titmice (P. bicolor). Most contact between the former two species occurred in these flocks. While in flocks, Brown—headed Nuthatches foraged most heavily on the distal parts of limbs and on twigs, Pine Warblers on proximal parts of limbs. When alone, Brown—headed Nuthatches foraged more heavily on trunks and proximal parts of limbs than they did when Pine Warblers. When pine seeds were abundant, Brown—headed Nuthatches fed upon them heavily and regularly ventured to large limbs and trunks to crack seeds, causing increased hostilities with Pine Warblers. Attempts to crack seeds where bark was not sufficiently rough to permit adequate anchoring met with little success. Pine Warblers fed upon pine seeds much less frequently than did Brown—headed Nuthatches. During the height of seed abundance, Brown—headed Nuthatches lingered behind mixed flocks and often became separated from them. More competition for food apparently exists between Brown—headed Nuthatches and Pine Warblers than between either of these species and others. The noticeably different foraging distribution of the two species when together and apart is probably largely the result of the presence or absence of the other. Dividing the habitat in each other's presence avoids fighting over a similar foraging station. Abundant food sources may cause this system to break down.

Comparative Biosystematics and Life History of the Nuthatches Sitta pygmaea and Sitta pusilla, by Robert A. Norris [Review

Comparative Biosystematics and Life History of the Nuthatches Sitta pygmaea and Sitta pusilla, by Robert A. Norris [Review

Unusual Nesting Behavior of the Brown-Headed Nuthatch

Unusual Nesting Behavior of the Brown-Headed Nuthatch

Nesting of Brown-Headed Nuthatch at Amelia, Va.

Nesting of Brown-Headed Nuthatch at Amelia, Va.

Large Set of Brown-Headed Nuthatch's Eggs

Large Set of Brown-Headed Nuthatch's Eggs