Comparative Breeding Behavior of Ammospiza caudacuta and A. maritimaWoolfenden, Glen Everett
Science
Comparative Breeding Behavior of Ammospiza caudacuta and A. maritima
Woolfenden, Glen Everett
Sparrows
When searching for food, Sharp-tailed Sparrows walk through the dense
black grass, deftly brushing stems aside with their bill as they go.
Open areas are generally traversed by rapid running. I never noticed
either species hopping. They stop to investigate openings in the matted
understory of grass, often sticking their heads into the holes. Many
times I saw these sparrows stretch or jump to pick insects from stems.
Many droppings, almost certainly those of Sharp-tailed Sparrows, were
present in areas of damp, matted grass. Females, when feeding young,
obtain most of the food near the nest; several times I saw birds catch
insects when they were within inches of their nest. Sharp-tailed
Sparrows feed also along the banks of pools and creeks, and along the
perimeters of marshes. Sharp-tailed Sparrows seem to be less restricted
in the types of feeding habitats they can use than are Seaside
Sparrows.
Seaside Sparrows always returned to the edge of the marsh to procure
food, according to my observations. The birds at Lavallette fed
extensively on noctuid moths. In the feeding territories of two pairs
of Seaside Sparrows, along the strip of washed-up eel grass, I found at
least 40 wings of these moths. In several instances the four wings of
one moth were lying close together in the same relative position in
which they had been on the animal. Legs and pieces of thorax were also
discarded occasionally. I watched adults take these moths from the
stems of the smooth cord-grass and snip the wings off with their bills.
Moth wings were present in the other feeding territories, but not in so
great a quantity. Once I saw a female return to the nest with a spider
in her bill. Spiders were abundant throughout the marsh.
Dwight (1900:193) was surprised that the two species living in the same
environment, and therefore suffering equally from abrasion from the
coarse marsh grasses, should have a different number of molts per year.
The Sharp-tailed Sparrow has a complete pre-nuptial, as well as a
complete postnuptial, molt. The Seaside Sparrow has only a postnuptial
molt, the nuptial plumage being acquired by wear. My observations of
the feeding habits of the two species indicate that they do not live in
precisely the same environment. The Sharp-tailed Sparrow, which has two
complete molts annually, generally forages in dense, abrasive
vegetation. The Seaside Sparrow, which has but one molt each year,
forages in relatively open areas.
Several times I saw adult Seaside Sparrows fly from their nests toward
the feeding territories with fecal sacs in their bills. On the feeding
grounds, I found several of these sacs discarded near the moth wings. I
saw also female Sharp-tailed Sparrows leave their nests with fecal
sacs. I did not see sparrows of either species swallow fecal sacs.
Public-domain text, read in full here on John Shaqi.
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