Readers’ wildlife photos

Today is Sunday, meaning that we get a themed bird post from biologist John Avise. John’s notes and IDs are indented, and you can enlarge the photos by clicking on them. John’s post is a sequel to his series last week on sexually dichromatic birds (link below).

Avian Sexual Monochromatism

Last week’s post showcased several birds with pronounced plumage color differences between males and females.  However, not all birds are sexually dichromatic; in many species it is nearly impossible for us to distinguish the sexes based on plumage coloration alone.  Perhaps sexual selection is weak or ineffectual in such species, or perhaps females use other cues when choosing partners.  For example, Northern Mockingbird males with more varied songs tend to be more successful in attracting mates.  Also, at least some sexually monochromatic species have a monogamous mating system that presumably lessens the degree of sexual selection (and, hence, of sexual dimorphism).  In any event, this week’s post offers several photos of Passeriformes species in which it’s difficult or impossible to specify an individual’s sex simply by the visible color of its feathers (but remember too that birds, unlike us, can also see in the ultraviolet end of the light spectrum, so perhaps they might use some UV plumage cues).  I took all of these photographs in Southern California.

Bewick’s Wren (Thryomanes bewickii):

American Crow (Corvus brachyrhynchos):

California Towhee (Pipilo crissalis):

Loggerhead Shrike (Lanius ludovicianus):

Northern Rough-winged Swallow (Stelgidopyeryx serripennis):

Song Sparrow (Melospiza melodia):

White-breasted Nuthatch (Sitta carolinensis):

Oak Titmouse (Baeolophus inornatus):

Say’s Phoebe (Sayornis saya):

House Wren (Troglodytes aedon):

Black Phoebe (Sayornis nigricans):

Hermit Thrush (Catharus guttatus):

Mountain Chickadee (Poecile gambeli):

Cassin’s Kingbird (Tyrannus vociferans):

Black-throated Sparow (Amphispiza bilineata):

Northern Mockingbird (Mimus polyglottos):