We measured wing length, tail length, bill dimensions, lengths of selected toes, presence of brood patches or cloacal protuberances, and estimated feather wear.
We banded 12 adult females, 11 of which had brood patches (one of these contained an unlaid egg in her lower abdominal region when banded).
The sides of the abdomen were examined for brood patches that develop in both members of a mated pair shortly before an egg is laid (Manuwal 1974), but none was detected in any of the birds.
The proventriculi of these 2 females contained prey and brood patches were not evident.
Throughout the study, four females developed brood patches
(indicative of breeding attempts).
chlorurus adults are sexually monomorphic in plumage, each adult with a brood patch was classified as female; this is based partly on the fact that in other towhees, only females have brood patches
and brood the young (Ehrlich et al.
The ventral thoracic and abdominal skin of each individual was examined for the presence of brood patches (Manuwal 1974).
That neither of the 2 females collected in late March and April 1971 had laid was confirmed by the absence of post-ovulatory follicles, and none of the 6, males or females, had developed brood patches that are generally functional in birds that lay eggs early in the season, but not in all late-breeding Cassin's Auklets (Manuwal 1974).
Captures of Scripps's Murrelet and Craveri's Murrelet off the colonies at night revealed (1) more non-breeders, but (2) the ratio of birds with and without brood patches was likely biased, because (3) adults spent less time on the ground than non-breeders, and (4) foraged apart from non-breeders (Whitworth and others 1997; Hamilton and others 2011).
2) Breeding adult Ancient Murrelets were distinguished from non- breeders on the basis of a combination of external measurements, differences in plumage and wear, development of the gonads, and presence or absence of brood patches (Sealy 1972, 1976).