512 NESTING OF THE BLUE-HEADED GREENLET 



fully fixed in a forked twig, presenting a neat and cozy appear- 

 ance, and symmetrically cup-shaped, though the exterior may 

 bristle with the projecting tassels of the pin-oak. The female 

 adjusts the materials which the male brings, and the structure 

 is completed in about three days. The eggs are laid one a day, 

 and incubation, which devolves solely upon the female, con- 

 tinues for 10 or 11 days, during which time the brooding 

 bird is supplied with nourishment by her dutiful mate. The 

 female is so unsuspicious, and so lacking in timidity, that persons 

 may pass and repass within ten feet of the nest without exciting 

 her distrust or causing alarm. Should her confidence, how- 

 ever, prove misplaced, and her home seem in danger of viola- 

 tion, she glides silently away, leaving to her valiant mate the 

 effort to resent the threatened intrusion and deter assault to 

 whose credit be it said, that he defends his home at the hazard 

 of his life. Both parents attend to the young, and are kept 

 busy enough in providing sufficient food. They seek and bring 

 to the nest the larvas of the various geometrid moths which 

 infest our trees; different kinds of flies and gnats, among them 

 species of Cynips, or gall-flies, as well as a few beetles a suffi- 

 ciently varied bill of fare, and one which attests the benefit 

 which these birds unconsciously confer upon us whilst they 

 care for their offspring. Only one brood is reared each season ; 

 the young are able to provide for themselves when they are 

 about 10 or 12 days old ; the female has then again to look 

 after herself, and the male becomes a selfish gourmand. Though 

 insects still form much of their fare, they now feed with gusto 

 on the berries of the Cornus and Viburnum, and reassert the 

 quiet and retiring disposition which the exigencies of the breed- 

 ing season temporarily hold in abeyance. 



Observing that in places frequented by this Yireo he had 

 often seen masses of pin -oak catkins which closely resembled 

 the nests themselves, Mr. Gentry questions whether some 

 principle of "protective mimicry" (as it is called by a certain 

 school) may not underlie the use of these substances as mate- 

 rials for the nests. " The utilization of such substances in the 

 manner of nests, from their fancied resemblance to loose clus- 

 ters of catkins, are best adapted to the security and well-being 

 of the species, and now constitute in certain localities the typi- 

 cal structure." 



Other and quite different styles of architecture are however 



