Nitrogen excretion by embryos of an altricial bird, the redwing blackbird (Agelaius phoeniceus)

Abstract

AbstractSmall quantities of urea and soluble urates are present in eggs of redwing blackbirds at oviposition, but no ammonia can be detected in eggs before the ninth day of a 12‐day incubation. Urea‐nitrogen accumulates relatively slowly in eggs during development, whereas urate‐nitrogen accumulates more rapidly. At hatching, 71% of the waste‐nitrogen accumulated in eggs is in the form of urates, 26% in urea, and 3% in ammonia. Thus, the general pattern of nitrogen excretion described for embryos of precocial birds applies also to those of an altricial species.