Sept. 1889.] 



AKD OOLOGIST. 



133 



A List of Birds in whose Nests the 

 Cowbird's Eggs Have Been Found. 



Having my attention called repeatedly to the 

 parasitical habits of the Cowbird {Molothrus 

 (iter) and having myself been fully convinced 

 that a large portion of the smaller birds are 

 annually prevented from raising a brood 

 through this bird's intrusions than is generally 

 supposed, I determined to watch them closely, 

 and commenced early the past spring to record 

 each instance of the finding of a Cowbird's 

 egg, or eggs, in the nest of another bird, and 

 the following is the resnlt of my observa- 

 tions. 



1. Sayornis phoebe. Pewee. One nest early 

 in April contained two eggs of the Cowbird 

 and three of the Pewee. Another found in 

 May contained damaged eggs of the owner and 

 two sound Cowbird's eggs. This nest had been 

 deserted some time. 



2. Einpidonax pusillus trailUL Traill's Fly- 

 catcher. A nest found in June contained one 

 egg of the Cowbird. 



:i. Spizella socialis. Chipping Sparrow. Six 

 deserted nests containing one or more eggs each 

 of the Cowbird have been recorded. These 

 nests usually contained an egg or two of the 

 Sparrow, which, like most of the Cowbird's, 

 had been chipped in the sides and part of the 

 contents gone. It is usually the habit of the 

 Cowbird to watch closely a nest which is 

 about completed, and when the first egg is 

 laid it generally deposits one or more of its 

 own. It will then revisit the nest in a day 

 or two and if the eggs are thrown out, which 

 quite often is the case, .another is deposited, 

 and the result will be that the bird is either 

 forced to desert its nest or hatch the in- 

 truder's egg. 



In this locality the Chipping Sparrow is a 

 great sufferer from the Cowbird's obstructive 

 habits. To illustrate the difficulty experi- 

 enced in this direction I give the substance of 

 my observations on a pair which built re- 

 peatedly in some evergreens about the prem- 

 ises. Their first nest as soon as completed 

 was noticed by a female Cowbird which had 

 been about for some time, and for several 

 days it made a visit to the nest (always when 

 the birds were away feeding) each day until 

 the first egg had been deposited, when im- 

 mediately a Cowbird's egg appeared, which, 

 when discovered by the Sparrows, was thrown 

 over the edge of the nest, but the next 

 day another was left by the Cowbii-d, which 

 was broken within the nest, perhaps in at- 



tempted efforts to remove it. This nest was 

 then deserted and another commenced not far 

 from it, which fared with materiallythe same 

 results. 



It was now quite late in the season, and 

 although the pair of Sparrows remained 

 about constantly they did not make further 

 attempts to raise a brood. I know of no in- 

 stance of the Chipping Sparrow's ever 

 hatching a Cowbird's egg. 



4. Spizella piixilla. Field Sparrow. A nest 

 containing a set of four eggs of the Sparrow 

 and one egg of the Cowbird found in June. 



5. Pipilo enjthrophthalmus. Towhee. I have 

 examined a dozen or more nests of this bird, 

 and with but one or two exceptions all con- 

 tained Cowbird's eggs. I think however that 

 very few nests are deserted by the owner on 

 this account, as the eggs closely resemble 

 their own, and the Cowbird is able to per- 

 form its intrusions quite successfully. On the 

 other hand the Towhee is more able to bear its 

 burden, without suffering much loss, than are 

 the small birds and it generally succeeds in 

 launching its double brood, 



6. Cardinalis cardbialln. Cardinal, The Red- 

 bird is not often troubled by this bird's mis- 

 deeds, but I once found and collected three nests 

 containing one, two and two eggs respectively 

 of the Cowbird while searching a swampy wood, 

 in the vicinity of Lima Lake, where a large 

 number were found nesting, 



7. Pas.serino cyanea. Indigo Bunting. On two 

 occasions I have found the Cowbird's egg in 

 this bird's nest. In neither case was the nest 

 deserted. 



8. Spiza americana. Black-throated Bunting. 

 But once recorded. One egg. May 30. The 

 nest deserted. 



9. Pirawja erijthromelas. Tanager, On May 

 5, A nest containing three eggs of this bird 

 and two of the Cowbird was observed, 



10. Piranga rubra. Summer Tanager, A 

 nest found July 16, containing two eggs of the 

 Cowbird and three of the Tanager in which 

 incubation was well advanced, 



11. Vireo olimceiis. Red-eyed Vireo, My 

 observations on the family Vireonidae in this 

 connection were made as thorough and com- 

 plete as possible, and they at once show that 

 in this family are the Cowbird's greatest vic- 

 tims. No birds, when burdened with a Cow- 

 bird's eggs, are more helpless than the Vireos. 

 Of the Red-eyed Vireo I have found six 

 nests, and out of this number four contained 

 eggs of the Cowbird and the other two incom- 

 plete sets, I have never found over four eggs 



