Date: 7/31/20 11:10 am
From: Pam Hunt <biodiva...>
Subject: [NHBirds] Of Cones and Cuckoos...
Among whatever patterns emerge in NH's avian world this summer, two stand
heads above the other: the large influxes of cuckoos (particularly
Yellow-billed) and Red Crossbills.

A post to the "Upper Valley Birders" email list this morning, combined with
some observations yesterday, have prompted me to chime in on the fascinating
subject of how birds respond to food supplies.

Let's start with cuckoos. A colleague at Dartmouth posted something about
caterpillars to a Valley News blog
igan-about-f2258bddfa864ded9aede74c1b0fd2f1), the gist of which is that
researchers at the Hubbard Brook Experimental Forest (Woodstock, NH) are
seeing their highest caterpillar numbers in 20 years. This is great news for
forest birds, since it means lots of yummy squishy things to feed their
young, and they might need all the help they can get this year because of
the potential for high nest predation from chipmunks (in turn a result of
last fall's bumper acorn crop, but I digress). Cuckoos are caterpillar
specialists, particularly on hairy ones (they have adaptations to reduce the
irritation these hairs can produce). You'll see more cuckoos in years with
gypsy moth or tent caterpillar outbreaks, which are actually both a little
below the radar this year. LAST YEAR, however, there was a small gypsy moth
outbreak in the Connecticut River valley south of here, and I heard or saw
multiple YB Cuckoos in Connecticut and western Mass (despite only being in
each for a single weekend). Presumably those cuckoos had a productive
breeding season, and this year we might be seeing the result: more cuckoos
than usual returning from the south. In combination with lots of food (even
if not always hairy), these cuckoos are sticking around and breeding in
higher than usual numbers, and their offspring will likely wander off to
whatever region in the Northeast has abundant food in 2021.

Crossbills are even more notorious for their wanderings, all in response to
the boom/bust nature of cone crops in pines, spruces, hemlocks, and other
conifers. They'll depart an area when food is scarce, and show up in others
when it is abundant. Last summer there was a nice movement of Red Crossbills
into western and northern New Hampshire that built up into the fall and
winter, eventually leading to birds nest building in January and February
(since they feed their young conifer seeds, crossbills have a much less
constrained breeding season!). Late this spring, when we were all hunkered
down avoiding a pandemic, they started to appear in southern NH,
particularly the highlands of the Monadnock Region
&yr=cur&byr=2020&eyr=2020). By June they'd started spilling north into the
Concord area, and as July comes to a close they've filled in most of the
state except the immediate seacoast and along the Massachusetts border in
the southeast (
&yr=cur&byr=2020&eyr=2020). And once again they are starting to show signs
of nesting. THESE crossbills could be the same ones that nested in the north
over the winter, their offspring, or a combination of the two, and they are
here because of a bumper crop of white pine cones (there are also some good
spruce crops in the north). Yesterday morning I was listening to at least 6
Red Crossbills in Brookline and Mason with Chris McPherson, and then went
south of the border to Townsend, MA, only 5 miles away. I heard ONE Red
Crossbill there in about half an hour, but no more over the next 5.5 hours
of exploring Pepperell and Groton. During this time I was struck by the near
ABSENCE of cones on the white pines, which probably explains the paucity of
crossbills, but one can only wonder why the "sudden" shift in pine
productivity over such a short distance. Is the absence of crossbills along
the Mass border in southern Rockingham County a result of similar poor cone
crops, or are there fewer birders there? I suspect the former since
northeastern Mass is FULL of birders, and that Mar-Jul crossbill map from
eBird shows almost no crossbills east of Worcester.

How long will these crossbills stay? Probably at least a few months, at
which point they'll wander off in search of the next good cone crop
somewhere in North America. To find a crossbill, you'll definitely need to
familiarize yourself with their distinctive "jip jip jip" flight call, since
while they're pretty common right now I've still only seen four perched, and
sometimes never see them at all as they fly high above. Recording these
flight calls is also valuable, since there is some fascinating variation in
calls that's associated with morphological variation tied to favored cones
for foraging. So far during this current invasion, birders have documented
four of the eight call types known from the U.S., but THAT is a story for
another time (although see:

As Bob Quin would say: "Fun with Birds!"

Pam Hunt


"The most dangerous worldview is the worldview of those who have not viewed
the world."

- Alexander von Humboldt

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