Nesting ecology and ontogeny of hatchling Neotropic Cormorants (Phalacrocorax brasilianus)




Bock, Jennifer

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The Neotropic Cormorant is one of the most widely ranging members of its genus. The justification of lethal control of piscivorous birds to protect fisheries requires a firm understanding of the population status and dynamics of the problem species. The nests of 7 pairs of Neotropic Cormorants were observed to determine: parental behavior when adding material to the nest; parental behavior prior to and during hatching; brooding behavior; number and duration of feeding intervals and how the age of chicks affects these numbers; behavior of chicks during feeding and how hatch order and age affect this behavior; and interaction among chicks in the parents' absence. Incubating adults became agitated a few hours prior to the hatching of each egg. Eggs hatched 1 to 2 days apart. Adults removed eggshells after hatching. Brooding continued without a break after hatching for several days. Parents took turns brooding the chicks. Nest repair occurred frequently in the first 2 weeks after hatching, then ceased. The number of feeding intervals per observation period ranged from O to 4. There was a general trend for feeding intervals to increase in frequency after sunrise until the peak in feeding activity at 3 to 4 hours after sunrise. The number of feeding attempts per feeding interval ranged from 1 to 11, with a mean of 2.18. The highest number of feeding intervals per day occurred 1 or 2 days after hatching, with the number of feeding intervals decreasing steadily until fledging. The mean number of feeding attempts per feeding interval also declined as the chicks aged. The latest observed feeding occurred on day 60. Most chicks fledged 47 days after hatching. The mean number of chicks fledged per nest was 2.71. No chick or adult mortality was observed.



neotropic cormorant, ontogeny, hatchling cormorants, piscivorous birds, Phalacrocorax brasilianus


Bock, J. (2004). Nesting ecology and ontogeny of hatchling Neotropic Cormorants (Phalacrocorax brasilianus) (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.


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