The response of avian chewing lice (Psocodea: Phthiraptera) loads to early-1900s urbanization in the Western United States

Using a historical record of bird specimens, we examined the effect of
historical urban environments on parasitic interactions by measuring the
abundance of ectoparasites on two bird species: House Finch and Hairy
Woodpecker. We counted adult chewing lice and their nits from museum study
skins of these two species, which were collected in the western United
States from 1900 to 1932. Our urbanness metric for each specimen’s
collection site and year was extracted from the Built-Up Footprint Area
dataset, which measures the area covered by human structures each decade.
To count lice, we searched 104 House Finch and 56 Hairy Woodpecker study
skins (hosts) from the UCLA Dickey Bird and Mammal Collection. Specimens
were collected between 1905 and 1932 across the states of Washington,
Oregon, California, Idaho, Nevada, and Arizona. We documented two louse
species parasitizing House Finches (host n = 104) and four parasitizing
Hairy Woodpeckers (host n = 56), as well as abundant nits which were not
identified to species. Of the 104 House Finches, 32 (31%) hosted Brueelia
thorini and 26 (25%) hosted Philopterus sp., including 11 (11%)
which hosted both species. Of the 56 Hairy Woodpeckers, just 1 (2%) hosted
Menacanthus sp., and this individual hosted 6 Menacanthus sp. and
27 total lice. Additionally, 7 (13%) woodpeckers hosted Brueelia straminea
s. lat., 4 (7%) hosted Picicola snodgrassi, and 11 hosted P. auritus s.
lat.