Plasma testosterone levels during the testicular cycle of the redwinged blackbird (Agelaius phoeniceus).

Ql#NEBAL AND COMPARATIVE ENDOCRINOLOGY i&i, 352-363 (1974) Sex-Steroid Formation in Gonadal Tissue Homogenates During the Testicular Cycle of the Redwinged Blackbird (Age/&us phoeniceus)

Fluctuations in the in vitro metabolism of pregnenolone-‘II and progesterone-“C were studied in the testes of captive, photoinduced, adult Redwinged Blackbirds (Age&w phoeniceus) during the gonadal cycle. Starting material utiliration was high 03799%) during the photosensitive stage (breeding period), decreased during the regressive stage, and leveled off at about 40% in the refractory stage. T...

Maternally derived yolk testosterone enhances the development of the hatching muscle in the red-winged blackbird Agelaius phoeniceus.

Hatching asynchrony in avian species often leads to the formation of a size hierarchy that places last-hatched nestlings at a significant disadvantage. The hatching muscle (musculus complexus) is responsible for breaking the shell during hatching and for dorsal flexion of the neck during begging. An increase in its strength in last-hatched nestlings could mitigate the effects of hatching asynch...

Predators on Red-winged Blackbird nests in eastern North Dakota

Predation has consistently been identified as the most common cause of nest failure for Redwinged Blackbirds (Agelaius phoeniceus). During May and June, 2000 and 2001, we used infrared-triggered camera systems to identify potential nest predators on artificially relocated Red-winged Blackbird nests in eastern North Dakota. For some of the species observed, these observations represent the first...

Generalizability of Artificial Neural Network Models in Ecological Applications: Predicting Nest Occurrence and Breeding Success of the Red-winged Blackbird Agelaius phoeniceus

17 Separate artificial neural network (ANN) models were developed from data in 18 two geographical regions and years apart for a marsh-nesting bird, the red-winged 19 blackbird Agelaius phoeniceus. Each model was independently tested on the spatially and 20 temporally distinct data from the other region to determine how generalizable it was. The 21 first model was developed to predict occurrenc...

Acoustic directionality of red-winged blackbird (Agelaius phoeniceus) song relates to amplitude and singing behaviours