Chewing lice (Phthiraptera: Amblycera and Ischnocera) infesting woodpeckers and sapsuckers (Aves: Piciformes: Picidae) in Manitoba, Canada

Five species of woodpeckers (Piciformes: Picidae) in Manitoba, Canada were examined for chewing lice (Phthiraptera: Amblycera and Ischnocera): downy woodpecker (DOWO) (Picoides pubescens (Linnaeus), n=56), hairy woodpecker (HAWO) (Picoides villosus (Linnaeus), n=32), pileated woodpecker (PIWO) (Dryocopus pileatus (Linnaeus), n=12), northern flicker (NOFL) (Colaptes auratus (Linnaeus), n=223), and yellow-bellied sapsucker (YBSA) (Sphyrapicus varius (Linnaeus), n=192). Seven species of lice were collected (total number=40 613): Menacanthus pici (Denny) from all species of woodpeckers, Brueelia straminea (Denny) from both species of Picoides Lacépède, Penenirmus jungens (Kellogg) from northern flicker, Penenirmus auritus (Scopoli) from all species of woodpeckers examined except northern flickers, Picicola porisma Dalgleish from northern flickers, Picicola snodgrassi (Kellogg) from both species of Picoides, and Picicola marginatulus (Harrison) from pileated woodpeckers. Prevalence for total louse infestation ranged from 32.3% to 85.7% (NOFL>YBSA>PIWO>DOWO>HAWO). Mean intensity for total lice ranged from 29.2 to 232.4 (PIWO>NOFL>HAWO>YBSA>DOWO). Infestation parameters for each louse/host combination are provided. Distribution of louse infestations was highly aggregated. In all louse/host combinations, either females were more prevalent than males or there was no significant deviation from 50:50. There was a tendency for louse species to co-occur on the same host specimen.

Effects of Urban Sprawl on Snags and the Abundance and Productivity of Cavity-Nesting Birds

We investigated the occurrence of, and relationships among, snags and cavity-nesting birds in the rapidly urbanizing region around Seattle, Washington in 2001 and 2002. We measured the density of snags in 49 sites (1-km2 “suburban landscapes” that included built and forested portions), and determined the diameter, height, decay status, and species of individual snags. We spot-mapped territories and observed nests of cavity-nesting birds at a stratified, random subsample of 13 sites. Snags, especially red alder (Alnus rubra), were abundant in sites' forested portions, but rare in the built portions. Snag density was positively correlated with density of live trees. Snags in built versus forested portions were similar in all attributes except decay, which was more advanced in forested areas. In the oldest suburbs (60–80 years old), snags in forested portions were larger, more decayed, and more likely to have broken tops than those in younger suburbs (2–20 years old). Cavity-nesting bird species richness and equity of individuals per species was highest in suburban landscapes where remaining forest was not fragmented, but adjacent to highly intermixed urban and urban-forest land covers. Suburban landscapes with highly interspersed land covers had higher densities of Black-capped Chickadees (Poecile atricapillus), Red-breasted Nuthatches (Sitta canadensis), Northern Flickers (Colaptes auratus) and Downy Woodpeckers (Picoides pubescens); suburban landscapes with higher percentages of forest had higher densities of Brown Creepers (Certhia americana), Chestnut-backed Chickadees (Poecile rufescens), Pileated (Dryocopus pileatus) and Hairy Woodpeckers (Picoides villosus). Red-breasted Sapsucker (Sphyrapicus ruber) densities were positively correlated only with the density of snags. All study sites had low bird densities compared to wildlands, presumably due to the relative lack of live trees and snags. Cavity-nesting birds bred successfully in all landscapes; seven of the nine species produced fledglings in >50% of their nesting attempts. Snags important for nesting were larger in diameter, taller, and more decayed than expected based on availability. Snags with active nests also had evidence of previous use, fungal conks, broken tops, and substantial bark. Efectos de la Expansión Urbana sobre la Abundancia y la Productividad de Aves que Nidifican en Cavidades Resumen. Durante el 2001 y 2002, investigamos la presencia de, y la relación entre, troncos muertos y aves que nidifican en cavidades en los alrededores de Seattle (Washington), una región que está urbanizándose rápidamente. Medimos la densidad de troncos en 49 sitios (1-km2 de “paisajes suburbanos” que incluyeron ambientes edificados y bosques) y determinamos el diámetro, altura, estado de descomposición y especie de troncos individuales. Mapeamos los territorios mediante registros puntuales y observamos los nidos de aves que nidifican en cavidades en una sub-muestra estratificada y al azar de 13 sitios. Los troncos, especialmente de Alnus rubra, fueron abundantes en las áreas con bosque, pero raros en las áreas edificadas. La densidad de troncos se correlacionó positivamente con la densidad de árboles vivos. Los troncos de las áreas edificadas y de las áreas con bosque fueron similares en todos sus atributos excepto en su descomposición, que fue más avanzada en los sitios boscosos. En los suburbios más viejos (60–80 años), los troncos en las áreas con bosque fueron más grandes, estuvieron más descompuestos y presentaron mayor probabilidad de tener sus extremos rotos que aquellos presentes en los suburbios más nuevos (2–20 años). La riqueza de especies que nidifican en cavidades y la equitatividad de individuos por especie fueron mayores en los paisajes suburbanos donde el bosque remanente no estaba fragmentado, sino adyacente a coberturas con una gran mezcla de sitios urbanos y sitios en la transición bosque-ciudad. Los paisajes suburbanos con coberturas ampliamente entremezcladas presentaron mayores densidades de Poecile atricapillus, Sitta canadensis, Colaptes auratus y Picoides pubescens; los paisajes suburbanos con porcentajes más altos de bosque presentaron mayores densidades de Certhia americana, Poecile rufescens, Dryocopus pileatus y Picoides villosus. Las densidades de Sphyrapicus ruber sólo se correlacionaron positivamente con la densidad de troncos. Todos los sitios de estudio tuvieron bajas densidades de aves comparados con áreas silvestres, debido presumiblemente a la carencia relativa de árboles vivos y troncos. Las aves que nidifican en cavidades criaron con éxito en todos los paisajes; siete de las nueve especies produjeron volantones en >50% de sus intentos de nidificación. Los troncos importantes para nidificar fueron más grandes en diá metro y altura y estuvieron más descompuestos que lo esperado con relación a su disponibilidad. Los troncos con nidos activos también presentaron evidencias de uso previo, deformaciones producidas por hongos, copas rotas y bastante corteza.

Interseasonal and Intersexual Resource Partitioning in Hairy and White-Headed Woodpeckers

Foraging behavior in the closely related Hairy (Picoides villosus) and White-headed (P. albolarvatus) woodpeckers was examined in an area of sympatry to evaluate interseasonal and intersexual resource use. Similar foraging heights were observed for each species-sex sample during summer, but significant differences were evident during winter. Male and female White-heads maintained similar relative foraging heights between seasons, whereas male and female Hairies foraged relatively higher during winter. Use of tree species differed significantly for each class between seasons, except for male Hairies. Differences in foraging substrates and tree health also were noted interseasonally. All foraged at similar times of day during summer, but negative relationships occurred between times of foraging during winter; foraging times were significantly different between male Hairies and White-heads. A general trend toward decreased overlap in foraging behaviors during winter was a reflection of concentration of foraging activities on live incense cedar (Calocedrus decurrens), especially by female White-heads. This change apparently was due to the presence of an abundant and accessible prey (incense cedar scale, Xylococculus macrocarpae) on cedar. Behavioral shifts in foraging activities may be related to the differential ability to extract prey as a function of bill morphology; such an idea can be extended to intersexual as well as interseasonal considerations. Thus, segregation of foraging activities in these two woodpecker species may be attributed to morphological differences and habitat complexity rather than to competitive interactions dictated by resource limititions.