We compared growth rates and adult morphological traits in two sympatric cormorant species, the pygmy cormorant (Phalacrocorax pygmeus) and the great cormorant (P. carbo sinensis), in Israel. The smaller P. pygmeus exhibited higher developmental rates than P. carbo sinensis, as expressed in the growth rate constant (K) of body mass and of various body parts (bill, wing, tarsus, primaries, and tibia lengths). The consequences of the higher developmental rate of P. pygmeus are early fledging and a relatively low body mass of fledlings. We suggest that several proximate ecological and developmental factors such as risk of nest predation, body temperature regulation, and hydrodynamics act in concert to promote rapid development in chicks of P. pygmeus. However, the four-fold lower body mass ofthe adult P. pygmeus is probably the most important physiological constraint that might explain its rapid growth rate in comparison with P. carbo sinensis. The body mass and the size of various body parts of adult P. carbo sinensis are much higher than those of adult P. pygmeus. This difference in adult morphological attributes, together with the marked differences in growth rates between the two species, should be reflected in different ecological functions that promote ecological segregation between them. Therefore, the conservation policies and future practical solutions of the cormorant-fisheries conflict should be species-specific.
Bibliographical noteFunding Information:
This research was supported by grants from the Israeli Ministry of Science, from the Technion-Haifa University Fund, from the Technion SAFRAM Fund, and from the Forchheimer Foundation (to M.S.). We are grateful to Prof. Daniel Weihs for his helpful comments, Ofer Shmueli, Zvi Shmueli, Abraham Dagan, Yahali Dagan, and Ruth Almon for their help in obtaining and raising the cormorant nestlings during the study; to Shoshana Goldenberg for her technical assistance; to the staffs of the Safari Park in Ramat Gan and the Biblical Zoo in Jerusalem for providing us with nestlings and eggs; and to the fishermen in the kibbutzim Hazorea, Maoz-Haim, Geva, Ma’agan-Mikhael, Baram, and Kefar Yehoshua for the fish supply during the study.
ASJC Scopus subject areas
- Animal Science and Zoology