Characteristics of Eggs and Hatchlings of the Altricial Double-crested Cormorant (Phalacrocorax auritus) and the Precocial Ring-billed Gull (Larus delawarensis)
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Authors
Reed, Wendy L.
Issue Date
1992
Type
Thesis
Language
en_US
Keywords
Alternative Title
Abstract
Two general developmental patterns are used to classify birds; altricial
birds hatch at a relatively early stage of development, and precocial birds hatch
at an advanced stage of development. Along with developmental differences
between these two bird types there are intrinsic differences between natural
allotment of yolk, albumen and shell to these eggs and the use of these
components throughout incubation, and in the construction of the egg shell,
which prescribes how much water is lost to the environment. I conducted a
study of egg shell characteristics, egg components and hatchling components of
the Ring-billed Gull (Larus delawarensis) and the Double-crested Cormorant
(Phalacrocorax auritus), which are representative of semi-precocial and altricial
birds respectively. Freshly laid gull eggs are allotted considerably more yolk
and less albumen than fresh cormorant eggs, however at hatching a gull has used
a greater percentage of its yolk during incubation resulting in a yolk sac that is
much smaller than that of a cormorant. Both embryo types, however, use a
similar fraction of the total energy available at the start of incubation. Both eggs
lose similar amounts of mass due to evaporative water loss and at the end of
incubation cormorants have a greater percentage of water in the yolk sac and
relatively more water in their tissues when compared to gull hatchlings.
Metabolism of an altricial cormorant is notably less than that of a gull, but
conductances for the two types of eggs differ sufficiently such that the predicted
air cell gas tensions for these birds are similar. Thus, it has been demonstrated
with these species that characteristics of eggs, embryos, and incubation are
coordinated in such a fashion to produce interspecific similarities in the presence
of interspecific differences in their patterns of development.
With honors.
With honors.
Description
vi, 34 p.
Citation
Publisher
Kalamazoo College
License
U.S. copyright laws protect this material. Commercial use or distribution of this material is not permitted without prior written permission of the copyright holder.