Biology Reference
In-Depth Information
nestisasemicircularhalf-cupshape.Ifit'sbuiltatopabeamorotherbottomsupport,the
nestwillbemorecircular.Thefemalespendsalotoftimeshapingitwithherbelly.Once
the basic mud nest is constructed, they line it with grasses and then feathers. If things
go well, they may complete the nest in three days, but sometimes it takes as long as two
weeks, especially when the weather is unfavorable for gathering mud.
American Dippers,
birdsofgushingmountainstreamsintheWest,nestonclifffaces
orledges,sometimesbehindnoisywaterfalls.Malesmayhelpwithnestconstruction,but
insomepairsthefemaledoesitall.Theyseemtopreferusingwetmaterialsforbuilding.
In 1908, D. Gale described the process for one female, who rejected her mate's “des-
ultorycontribution”tohelp.Shebuiltthenest“fromthebottomup…thewallsraisedon
allsidesbyforcingthebuildingmaterial intothewallfrombelow….(F)ibersontheout-
side…lieloose,plush-like,toleadthewaterfromthedomeroofasfromahay-cock.As
thisworkonthewallsdries,theinsertionofotherplugs…knitsthewholedensely.…by
working from below, the lips or edges of the walls from all sides are closed up…. while
working on the lower side the bird lay flat on the floor, spread her wings for a purchase
and seemed to push with all her strength to ensure a well-caulked seam.” All this took
just one hour.
Bald Eagles
usually begin building a nest together months before producing eggs,
though in one case nest construction took only four days. Both mates gather fairly large
sticks, though the female usually takes the lead in placing them. Grasses, mosses, and
even cornstalks are used as fillers. Once the basic structure is in place, they'll add finer
materials,suchasSpanishmoss,andthenfeathers.Pairsworkonthenestthroughoutthe
nesting period and, especially, after their young have fledged each year and before the
next nesting season. A single Bald Eagle nest may remain in use for several decades. As
one bird dies, its mate will take a new mate, so what appears to be the same pair year
after year may actually be different ones.
Q Last spring I watched prairie-chickens from a blind. Later in the morning when
the chickens started leaving, suddenly Tree Swallows came in, flying back and forth
