. The oist . how the YellowWarbler will sometimes, when theCowbirds egg is laid before her own,build a second nest aibove and attach-ed to the first in order to get rid ofthe intruding egg, and at other timesbe able to kick it out of the nest rath-er than incubate it. This of course isa natural condition, with a bird whenhatched all ready to be able to ac-cept food given it by its foster par-ent. But the strange thing to me iswhy a bird in some species can neith-er distinguish weight, shape or color,as is very well shown by the experi-ments of Mr. Burgess. This year I tried putting two robins(
. The oist . how the YellowWarbler will sometimes, when theCowbirds egg is laid before her own,build a second nest aibove and attach-ed to the first in order to get rid ofthe intruding egg, and at other timesbe able to kick it out of the nest rath-er than incubate it. This of course isa natural condition, with a bird whenhatched all ready to be able to ac-cept food given it by its foster par-ent. But the strange thing to me iswhy a bird in some species can neith-er distinguish weight, shape or color,as is very well shown by the experi-ments of Mr. Burgess. This year I tried putting two robins(merula migratoria) in a kingbirdsI tyrannus tyrannus) nest which al-ready had two eggs. This as may beseen a case of a tyrannidae hatchingeggs of a species of turdidae, twowidely separated species. The king-bird flew back to the nest in a fewmoments and without noticing thechanged color and the nest beingmore filled with eggs settled downand began to incubate apparently per-fectly contented. 166 THE OOLOGISl. A few dajS later I investigated thenest and found the toird still settingon two of her own and two robinseggs never having laid any moreeggs; thus apparently showing thatthe bird had some control over lay-ing and had found that she had allthe eggs that she could cover. I again looked up my bird andfound two young birds of both spec-ies, but the robins were a very thinlooking pair of birds. Three daysafter this the birds were found in my mind the kingbird wasnot able to feed them in the rightway and not that she was able to tellthat they were not of her own if she could have told this howis it that she could not tell blue from brown spots on a white background. Besides the kingbird I tried chang-ing eggs with two warblers; twoclosely allied species. On June 18th I found the nest ofa black and white warbler (miniotil-ta varia) with four fresh eggs asshown in the accompaning this nest I found another nestbelonging to a pair of yellow warb-lors (
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