Overnighting of Golden-Crowned Kinglets during Winter

2 Pages·2003·1.3 MB·English

by  Bernd Heinrich

THE WILSON BULLETIN
A QUARTERLY JOURNAL OF ORNITHOLOGY
Published by the Wilson Ornithological Society
VOL. 115, NO. 2 June 2003 PAGES 1 13-224
Wilson Bull, 115(2), 2003, pp. 113-114
OVERNIGHTING OF GOLDEN-CROWNED KINGLETS
DURING WINTER
BERND HEINRICH'
—
ABSTRACT. The Golden-crowned Kinglet (Regulus satrapa) is the smallest insectivorous bird that over-
winters in boreal forests across North America from Alaska to Nova Scotia, where nights may last 16 h and
nighttime temperatures may fall below —40°C. I here provide the first documentation ofGolden-crowned King-
lets huddling in the field during winteron open branches. The birds forage until darkness anddo not necessarily
come back every night to the same site. Traveling in groups and huddling where they end up in the darkness
compensates forsmallbody size and potentialcompromises inforagingtime.Received28March2003, accepted
11 June 2003.
How 5- to 6-g kinglets can maintain energy capped Chickadees (Poecile atricapilliis).
balance to survive the long nights at low tem- Red-breasted Nuthatches (Sitta canadensis),
peratures has long been an enigma (Ingold and and occasionally Downy Woodpeckers {Pi-
Galati 1997). In winter these birds forage un- coides pubescens) and Brown Creepers {Cer-
interruptedly during the day, feeding predom- thia americana). Downy (Kilham 1983) and
inantly on hibernating caterpillars (Heinrich Hairy (P. villosus pers. obs.) woodpeckers ex-
and Bell 1995). Blem and Pagels (1984) cal- cavate holes in fall and winter for shelter dur-
culated that the fat reserves accumulated dur- ing the night, and Red-breasted Nuthatches
ing the day in midwinter are insufficient to routinely enter preexisting tree cavities at
support endothermy at ambient winter tem- dusk (pers. obs.). At least one small insectiv-
peratures for an entire night, suggesting that orous North American bird, the Verdin {Au-
the birds employ torpor, huddle, and/or spend riparus Jiaviceps) builds winter nests (Wals-
the night in uniquely insulated shelters. How- berg 1990) and therein huddles in groups. The
ever, Reinertsen et al. (1988), working with energy consideration of Blem and Pagels
Goldcrests {Regulus regulus) in Austria, (1984) suggested that kinglets may employ
found no torpor in captive (presumably well- some unusual strategy.
fed) birds that huddled at night (Thaler 1990) In dozens of attempts to follow kinglets
on open branches. Blem and Pagels (1984),
on the other hand, saw one Golden-crowned during late afternoon and evening, I occasion-
ally was successful in following them forover
Kinglet {R. satrapa) in the wild that appar-
an hour and until dark, but they always van-
ently entered a squirrel nest.
In the woods of western Maine, the site of ished from sight as it was getting too dark to
the present observations, kinglets routinely see (i.e., they foraged until after sunset). Dur-
travel in mixed species flocks with Black- ing early January, 1995, I had on three occa-
sions followed a group of three kinglets at
dusk to where I had previously located two
' Dept, ofBiology, Univ. ofVermont, Burlington, VT red squirrel {Tamiasciurus hudsonicus) nests.
05405-0086, USA; e-mail: [email protected] The birds “disappeared” in a balsam fir {Abi-
113
114 THE WILSON BULLETIN • Vol. 115, No. 2, June 2003
es balsamifera) thicket. No kinglets could be feathers. One bird jerked its head up when I
flushed from the squirrel nests, nor were any jiggled the roost, and then just as quickly re-
seen to leave them at dawn. tracted it back into its fluffed out feathers.
On 19 December, 2000, after a night of Temperatures then were -4° C, but later that
heavy winds with driving sleet and snow, I night declined to —10° C. I again checked the
flushed two kinglets in the predawn darkness birds at 19:30 and in the predawn at 04:30.
from near the ground out of a snow-covered As before, the tail positions had not shifted
brush pile. No kinglets returned to this shelter and rapid breathing movements were visible;
during the next two evenings. the birds apparently were not in torpor. No
On 25 November 2002, I saw three kinglets birds were seen at that site during the next
m
while I was perched about 12 up in a spruce week.
(Picea sp.) tree. As it was starting to get dark Hundreds of observations of Golden-
(10 min past the official sunset of 16:05 EST) crowned Kinglets during winter in western
I heard “tsee” calls and then saw a kinglet Maine indicated that these birds always trav-
land on a twig near me. It turned around sev- eled in groups of two to four. The kinglets
eral times and a second onejoined it. The two commonly join up with chickadee flocks, but
pressed closely together and then stopped separate from them in the evening.
moving. The two then separated briefly after The present observations indicate that al-
a third bird arrived, but then they rejoined though microhabitats for nocturnal roosts are
each other to again huddle on the same likely important, overnighting sites may be
branch. The third bird called from a dense less specific and less important than the ability
neighboring balsam fir tree. The two then left to huddle quickly. Overwintering Golden-
their huddle andjoined the third one. All three crowned Kinglets apparently do not generally
birds then were invisible to me, but several return to the same site each night. Instead,
minutes later I heard “tsee” calls from near they forage until nightfall and huddle tightly
where they had disappeared from my view near where they end up.
into the dense foliage. ACKNOWLEDGMENTS
The following evening I again first heard
and then saw three kinglets in the same area, I thank C. R. Blem and J. L. Ingold for sharpening
and they again disappeared into the same my interest in these birds and for their comments on
the manuscript.
dense thicket. 1 monitored the area for two
more nights, occasionally hearing a kinglet LITERATURE CITED
but being unable to follow one. This site con- Blem, C. R. and J. E Pagels. 1984. Mid-winter lipid
tained a red squirrel nest. On each of the four reserves of the Golden-crowned Kinglet. Condor
evenings, the squirrel returned to its nest 86:491-492.
about 30—60 min before the kinglets arrived. Heinrich, B. and R. Bell. 1995. Winter food of a
I watched the nest closely but did not see any sKimnaglllet.inWsielctsiovnorBouulls.b1i0rd7,:55th8e-56G1o.lden-crowned
kinOglnettsheenteevreniti.ng of 27 December 2002, at IngolKdi,nglj.etL..Naon.d30R1. GinalTahtie.bi1r9d9s7.ofGoNlodrethn-Acmreorwinceda
16:20 (after the sun was below the horizon but (A. Poole and E Gill, Eds.). Academy of Natural
it was not yet dark) I saw three kinglets fly Sciences, Philadelphia, Pennsylvania, and the
into a brushy white pine {Pinus strohus). In American Ornithologists’ Union, Washington,
D.C.
less than a minute 1 fmound four kinglets hud- Kilham, L. 1983. Woodpeckers of eastern North
dled together about 4 above the ground un- America. Dover, New York.
der thick branches. I returned an hour later Reinertsen, R. E., S. Haftorn, and R. Thaler. 1988.
and from a step ladder examined the birds in Is hypothermia necessary for winter survival of
the beam of a flashlight. The birds’ chests the Goldcrest, Regiilus regulusl J. Ornithol. 129:
were pointing inward and their tails pointing 433-437.
outward in three directions. The birds showed Thaler, E. 1990. Die Goldhahnchen. A. Ziemsen Ver-
lag, Wittenberg Lutherstadt, Germany.
no reactions to repeated photographic flashes Walsberg, G. E. 1990. Communal roosting in a very
from a distance of 20 cm (Fig. 1) and their small bird: consequences for the thermal and res-
heads remained fully tucked into the back pirating gas environment. Condor 92:795-798.