[va-bird] Re: LA Waterthrush Sunday 6/27

Bob,

Maybe I'm misinterpreting your message, but my first thought was to protect
the reputation of North American cuckoos so that people wouldn't think they
are as bad as Old World cuckoos and our own nasty cowbirds that regularly
parasitize other birds' nests.

If you're saying that Yellow-billed Cuckoos regularly parasitize other bird
species' nests, I'd be interested to know the source of your information.
Since my understanding was that just the Old World cuckoos were nest
parasites, your comments prompted me to do some research.  According to The
Sibley Guide to Bird Life and Behavior (and other sources I have here at the
house), "North American cuckoos rarely parasitize other birds' nests."  But
"brood parasitism within a species (intraspecific parasitism) is fairly
widespread," especially if a female loses her nest while an egg is
developing in her reproductive system.  Sibley does say that "Yellow-billed
and Black-billed Cuckoos occasionally parasitize other birds' nests when
food is abundant.  Some observers assume that overly abundant food, as in a
cicada emergence, throws off the synchrony between nest-building and
egg-laying and leads to opportunistic parasitism.  In some cases, these
'parasitized' nests are really interspecific communal nests, with adult
cuckoos sharing duties with other species, such as the American Robin and
the Mourning Dove."

Another factor that Sibley mentions that influences how many cuckoos are
raised in a season is that "nesting Yellow-billed Cuckoos sometimes have
apparently unrelated helper males that can supply the young with up to 40
percent of their food, allowing the dominant pair to raise a second brood."
And that "during years of exceptionally high food abundance, Yellow-billeds
have raised three broods in a season."

Perhaps you didn't mean to give the impression that our cuckoos regularly
practice egg-dumping, but since that's how your email sounded to me, I just
wanted to clarify the facts.

Alyce Quinn
Roanoke, VA

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