Life histories of North American wood warblers, Part 1 (of 2)Bent, Arthur Cleveland
Science
Life histories of North American wood warblers, Part 1 (of 2)
Bent, Arthur Cleveland
Birds -- North America; Passeriformes; Wood warblers
Dr. F. A. E. Starr, in his notes from northern Ontario, also says that
any conifers are suitable nesting sites: "I have found only one
exception to the use of a conifer. This nest was built in a hawthorn,
and when I collected the nest, the birds moved to a cedar." A. D.
Henderson writes to me: "The myrtle warbler is a fairly numerous summer
resident at Belvedere, Alberta, and in the Fort Assiniboine District. It
nests mainly in the muskegs in tamarack and spruce trees, but
occasionally in deciduous trees close to a muskeg." The nests are mostly
from 10 to 15 feet up. One nest was in a jack pine, "in a bunchy growth
at the end of a limb." Baird, Brewer, and Ridgway (1874) state that
MacFarlane found nests on the ground in the Anderson River region.
_Eggs._--Most observers agree that four or five eggs form the usual set
for the myrtle warbler. Tufts (MS.) says that "five eggs are more
commonly found than four." Dr. Starr says in his notes that "four eggs
are rarely laid, two and three being the usual numbers, while sometimes
only one is laid, along with those of the cowbird." This is probably an
abnormal situation in which the cowbird fills the nest with its own
eggs, leaving little room for those of the warbler.
The eggs are ovate to short ovate and slightly glossy. The ground color
is creamy white and is speckled, spotted, or blotched with "auburn,"
"argus brown," "Brussels brown," "chestnut brown," or "cinnamon-brown,"
with undermarks of "light brownish drab," "vinaceous gray," or "purplish
gray." Generally the spots are concentrated at the large end, forming a
wreath, but some are marked all over and may also have a few scrawls of
blackish brown. I think the handsomest are those having the rich creamy
white ground almost immaculate except for a solid wreath, around the
large end, of spots and blotches of the browns overlapping and
intermingled with the undertones of gray, so that they resemble somewhat
the eggs of the wood pewee. On lightly marked eggs the drab or gray
spots are the most prominent. The measurements of 50 eggs average 17.5
by 13.3 millimeters; the eggs showing the four extremes measure =20.3=
by 13.2, 17.9 by =14.8=, =14.8= by 12.9, and 16.0 by =12.4= millimeters
(Harris).
_Young._--The incubation period for the myrtle warbler is from 12 to 13
days and the young remain in the nest normally from 12 to 14 days.
Incubating the eggs and brooding the young is apparently done entirely
by the female, but both parents are active in feeding the young and in
cleaning the nest. Mrs. Nice (1930a), with the help of Miss Lucille
Baker, watched a nest containing young for a total of 19 hours, over a
period of 6 days. On the first day the female brooded 25 percent of the
time, but less later on; the brooding periods averaged 9 minutes.
Public-domain text, read in full here on John Shaqi.
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