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 (https://www.notion.so/What-are-all-those-half-eaten-beech-leaves-on-Mt-Card 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 (https://ebird.org/nh/map/redcro?neg=true <https://ebird.org/nh/map/redcro?neg=true&env.minX=-75.54551782295202&env.mi nY=42.126744408811525&env.maxX=-65.85191453084444&env.maxY=45.17428972131046 5&zh=true&gp=false&ev=Z&mr=on&bmo=3&emo=5&yr=cur&byr=2020&eyr=2020> &env.minX=-75.54551782295202&env.minY=42.126744408811525&env.maxX=-65.851914 53084444&env.maxY=45.174289721310465&zh=true&gp=false&ev=Z&mr=on&bmo=3&emo=5 &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 (https://ebird.org/nh/map/redcro?neg=true <https://ebird.org/nh/map/redcro?neg=true&env.minX=-75.54551782295202&env.mi nY=42.126744408811525&env.maxX=-65.85191453084444&env.maxY=45.17428972131046 5&zh=true&gp=false&ev=Z&mr=on&bmo=3&emo=7&yr=cur&byr=2020&eyr=2020> &env.minX=-75.54551782295202&env.minY=42.126744408811525&env.maxX=-65.851914 53084444&env.maxY=45.174289721310465&zh=true&gp=false&ev=Z&mr=on&bmo=3&emo=7 &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: https://ebird.org/news/crossbills-of-north-america-species-and-red-crossbill -call-types/).
As Bob Quin would say: "Fun with Birds!"
"The most dangerous worldview is the worldview of those who have not viewed the world."