Assessment of foraging habitats of white-faced ibis near two important breeding colonies in eastern Idaho

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We studied the habitat use and foraging behavior of white-faced ibis (Plegadis chihi) in areas surrounding the Market Lake and Mud Lake Wildlife Management Areas in eastern Idaho, the two largest breeding colonies in the state, during the 2012 breeding season. We combined road-based driving survey routes with a random, spatially balanced selection of specific agricultural fields to survey from late April to mid-July in order to thoroughly survey a 22-km radius around both breeding colonies. We also conducted group activity and individual behavior assessments during this time period. We were particularly interested in gaining information on associations with specific crop types and irrigation (cultural) practices. Of 210 ibis observations, we documented 89% of foraging birds in natural wetlands and agricultural fields not irrigated by center pivots, even though 70% of the agricultural landscape was in center-pivot irrigation. Most agricultural fields used by foraging ibis were flood irrigated and had standing water at the time of use. Within these agricultural landscapes, alfalfa was the most common crop type used by foraging birds, although we did frequently observe foraging in other crop types. We also observed distinct distribution patterns around the two breeding colonies. Around Mud Lake most birds (~80%) were observed within a 12-km radius and in all directions from the colony. In contrast, just over half of the birds around Market Lake were found 12-22 km from the colony. There were consistent patterns across all observations and survey methods, namely that ibis used non-pivot fields (mostly flood irrigation) in a much higher frequency than what is available in the agricultural landscape and that birds within the 22-km radius of the Market Lake colony were observed almost exclusively to the south and southeast of the colony, reflecting the distribution of flood-irrigated agriculture in the area. The most common foraging distance (12–22 km) around Market Lake is greater than found in existing literature, suggesting that the foraging habitat is limited within 12 km of the colony and that the birds may need to travel further to find adequate foraging habitat. Over the course of this study, we also collected information on Franklin’s gull distribution and foraging habitat and found similar results. The results in this study point to the importance of flood-irrigated agriculture, as well as natural wetlands, as foraging habitats for white-faced ibis and other wetland species. We suggest that, in addition to protection of marshes where they nest, these feeding habitats are important to consider in future management and conservation of wetland species like white-faced ibis.

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ELECTRONIC FILE - Zoology

SWAP (2/19/2016) citation:
Moulton C, Carlisle J, Brenner K, Cavallaro R. 2013. Assessment of foraging habitats of white-faced ibis near two important breeding colonies in eastern Idaho. Boise (ID): Idaho Department of Fish and Game, Wildlife Diversity Program. 18 p. [accessed 2016 Feb 02]. http://iwjv.org/sites/default/files/upper_snake_white-faced_ibis_project....