Jan. 1S5)0.J 



AND OOLOCHST. 



7 



As t > tlie (Jowbinl occupying; tlie nest in 

 order to continue tlie duties of incubation, 

 temporarily abandoned by the owner of the 

 nest while in search of food, I cannot i)Osi- 

 tively assert, but once in an instance where 

 the mother bird was killed by ndstake, a fe- 

 male Cowbird was observed to leave the nest 

 the f(dlowin<;- day as if she were sittin<>-. The 

 eiin's were inc\ibated quite a week, and it was 

 eertain that she was not there for the purpose 

 of layin<;', foi- as yet 1 have never observed a 

 fresli eg<;' of the ("owbird in a nest where the 

 other efffi's were incubated, and very rarely 

 liave I seen an a<hlled Cow bird's es{>- in a nest 

 occupied by other eu}i,s. I feel certain that 

 the parent Cowbirds do at least keep the nests 

 occupied by their ejjfts under surveillance, and 

 this espionaji'e may extend to the <;uardian- 

 sldp of the tlediiiin<;' in an<l out of its foster 

 ]tarent"s home. It is not claimed t!i;it tlie 

 (\u\- Bnntiu};' is a brave bird, nor do I wish to 

 elevate it in tlie estimation of my readers, but 

 the natural instinct of protection of its 

 younji", exhibited to a marked de<;ree by many 

 species and more or less prominent as a trait 

 in nearly all. is shown by the Cowbird in at 

 least one case to my knowledjie. I refer to an 

 instance where I saw a Bluejay on the point 

 of despoilin>j the nest of a Vireo, diiven away 

 by a pair of (Cowbirds in a most valinnt man- 

 ner. On p;oin,o' to the nest a lar<;e overjirown 

 Cowbird was found occupyiui;" the larfjest 

 share of the structure, while a poor little Ked- 

 eyed Vireo occupied a small spnce at the 

 Itottom, and beneath his bif;' foster brother. 



It would be a very interestini"' fact could it 

 be demonstrated by the placin<; in continement 

 of an adidt Cowbird with its own olTspriui;'. 

 to watch the care exhibited by the natural 

 parent feedin<>- its (»wu youn<i. 



However, I have never taken a fem:ile whose 

 abdomen and breast indic-ated that incubiition 

 had been followed, neither have I seen an old 

 Cowbird feedinj;- younj;-. 



The period of incubation as observed by me 

 several times is between eleven and twelve 

 days. A <;reat many times that I attemi)ted 

 t.> accurately determine this i)eriod my })i-os- 

 pects have been upset fiom several untoward 

 events. The owner of the nest often left it, 

 either from my too freijuent j)resence or the 

 persecution of the imposter, but in two in- 

 stances the i)eiiod was quite nccurately de- 

 termined. From the fact that the owner cndy 

 besi'ins sittinu; after its complement was laid, 

 merely coverin<i' the eg^s at ni<;ht or perhaps 

 in inclement wenther before thnt time, it 



shows that even the most careful calculations 

 may be incorrect. This occurs, perhaps, from 

 the fact that the alien egg beinji' so much 

 lar<;er than the le<;itimate (mes, or that it 

 almost always rolls into the centre from its 

 superior wei<iht. In either case it comes into 

 more direct contact with the breast of the 

 lioverinji' bird. 



Furthermore, the Cowbird's ejiji's are always 

 laid soon after the first e<i<;' is obseive<l by the 

 parasite, and often before. In many complete 

 sets of Yellow Warblers, Vireos, and Redstarts, 

 where efj^gs of the sycophant also occupied the 

 nest, the following;' was observed on removin<'' 

 the contents: althou,<;h one, two, or all of the 

 legitimate ejif^s were fresh, the Cowbird's e<r<>- 

 or egffs were almost invariably slii^htly ad- 

 vanced in incubation. How cm this be ac- 

 counted f(M'.* First, the owner may as I su<r- 

 fjested, touc'.i tlie larjjjer eji'^is when coverin"" 

 all at niyht. It is quite possible, however, 

 that the anxious mother or father Cow Bunt- 

 in,t>' may incub:ite when the chance otters, at 

 the time when ej^j^s are lirst laid. Fiom two 

 well studied cases I have fairly concluded that 

 the period of incubation, as observed in tlie 

 sitting' of the iled-eyed Vireo and liedstait on 

 the e<ii;s of iiiDlot/trus, is between eleven and 

 twelve days in duration. I cannot say exactly, 

 as the younji' wcu> in both cases duly hatched 

 durinj;- the niu'ht, being there in the morninti', 

 and not a pip in the egj;s the night before. 



I feel (juite safe in saying that the old Cow 

 Buntings in some way influence the incubation 

 in favor of their own thick-shelled eggs in all 

 ca,ses where they are laid in the nests of small 

 birds. 



Will an iiiii)osed-on bird sit on a clutch 

 composed entirely of Cowbird's eggs? I think 

 in no case, but I know of two instances, both 

 in the case of Chewinks, where the rightful 

 eggs were rolled or thrown from the nest in 

 an advanced stage of incubation, either by the 

 Cow Bunting or in error by the aggrieved Che- 

 winks, where the young Cowbirds were ulti- 

 mately hatched in all security. 



Cases are common where suffering birds at^ 

 temi»t to build over the offending es:<i' or eiiirs. 

 often with success. The Yellow Warbler is 

 especially artistic aiul energetic in its efforts 

 to ciicumvent the dreaded incubus, and will 

 fre(iuently sacrifice one of its own eggs, or 

 more rarely two, in the effort to inhume the 

 detested aliens forced upon them. It is not 

 rare to lind these double-storied nests, and I 

 judge that there are many of them to-day in 

 collections, of which the owners are ignorant. 



