ttre ee Waa 2 bsOON By Cale K Tel N 3 
A few cowbirds are raised by inexperienced pairs of warblers, but this 
is the exception. I was unable to watch all nests from the time the eggs 
were laid until the young had left, but I found only two instances where 
the female warbler sat on cowbird eggs. In one nest, the warbler sat on 
two of her own and two cowbird eggs. This nest was destroyed before the 
eggs were hatched. In the other nest, one cowbird was hatched and raised. 
The cowbird is not the only menace of the nesting 
warbler. Too often, one of the others is man. If he 
disturbs the nest while it is being built, it is likely to 
be deserted and a new nest built nearby. When the 
nest is finished and the eggs are laid, the nest is less 
likely to be deserted. Instead, a great fuss is raised 
and the birds dart at the intruder and all but attack 
him. 
The efforts of both parents are rewarded when 
about two weeks after hatching, the young leave the 
nest. They stay in the nesting tree for about 24 hours 
and call for food, then remain in the nesting area for 
, several weeks. They are very shy at this time. 
In .fact, the yellow warbler is so shy most of the 
time that fortunately few people are aware that it is 
Arh Oleh telat aaa They do not look in a mosquito-infested area 
was rebuilt’ many tomes. that_is grown up with so much underbrush that one 
It is 5% in. high. It is finds it difficult to get through. If they did, they would 
cetera ee oo be amazed at the number of warblers to be found. 
One area which covers one square mile contained an 
estimated 40 pairs, which is not surprising, in view of the close proximity 
of some of the nests. 
When some doubt was expressed regarding my statement that two of 
the nests were only 15 feet apart, I found by measurement that the dis- 
tance between the small box elder trees in which they were situated was 
14 feet 7 inches, and the actual distance between the nests was 21 feet. The 
day the young left one nest, the first egg was laid in the other, so that 
nesting operations definitely were being carried on simultaneously. 
This is a most unusual record for birds not nesting in colonies. As a 
general rule, the tolerance of nesting pairs of the same species is several 
times this distance. 
I have learned many facts of this nature while watching the yellow 
warblers, even though my time was limited and my visits to the nests were 
of necessity rather irregular. It would be most interesting to see what 
could be accomplished in a study area similar to mine by four or five 
students who could arrange their time so that each nest could be visited 
at least once a day and each nesting pair observed for a full day. 
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