Illinois Natural History Survey Reports

              1
I LLINOIS
NATURAL
HI STORY
S U R V E Y R e p o r t s
Winter 2002
No. 370
I N S I D E
The Role of Insect
Flower Herbivory in
Native and
Restored Prairies
2
Turtle Research at the
INHS Great Rivers
Field Station
3
Soybean Aphids and
the Search for Natural
Enemies
4
Effects of Excluding
Birds on Illinois Prairies
5
Species Spotlight:
Mole Salamander
6
Naturalist's Apprentice:
Adaptations for Life
Underground
7
Continued on back page
Birds have evolved life history
traits that tend to maximize life-time
reproductive success, and
these traits include behavioral
responses to factors limiting re-productive
success. Behavioral
responses may be especially
important for birds breeding in
highly frag-mented
land-scapes
where
increased
nest preda-tion
and in-creased
brood
parasitism by
Brown-headed
Cowbirds can
greatly reduce
reproductive
success.
I studied
color-marked
populations
of Prothono-tary
Warblers
(Protonotaria
citrea) in the
fragmented
bottomland
forest of the
Cache River
watershed during 1993–2000 to
determine whether or not these
birds responded to nest predation
and brood parasitism in ways that
reduced the negative effects of
each. Experimental and non-ex-perimental
data demonstrated that
individual Prothonotary Warblers
returned to sites between years
in response to their reproductive
success (as limited by nest preda-tion).
Between-year site fi delity
increased with an increase in the
number of broods produced with
approximately 80% of double-brooded
males and females re-turning.
Individuals returned at
rates of approximately 30% and
50% when they produced zero or
one brood, respectively. Brood
parasitism by cowbirds reduced
the reproductive success of Pro-thonotary
Warblers as a result of
decreased hatching success of
warbler eggs and decreased sur-vival
of warbler nestlings. The
warblers accepted brood parasit-ism
and did not choose nest sites
inaccessible to cowbirds, defend
nests during the egg-laying pe-riod,
desert parasitized nests, or
avoid returning to sites where
they had been parasitized. The
results of this research indicate
that these birds may be able to
avoid chronically high rates of
nest predation by not returning to
areas where nest predation elimi-nates
nesting success. Protho-notary
Warblers, however, may
be especially vulnerable to eco-logical
traps where rates of nest
predation are low, levels of brood
parasitism are high, and they are
producing mainly cowbird young.
The Cache River Wetlands
(CRW) bottomland forest restora-
Responses to Nest Predation and Brood
Parasitism in a Migratory Songbird
Two Prothonotary Warblers, brilliant yellow inhabitants of Illinois. Photo courtesy of Bryan Holliday