Composition, Structure, and Dynamics of Mixed-Species Foraging Aggregations in a Southern New Jersey Salt Marsh

• Published in: Colonial waterbirds 1992-01, Vol.15 (1), p.66-74
• Main Author: Master, Terry L.
• Format: Article
• Language: English
• Subjects: Aggregation; Aves; Brackish; Fish; Flocks; Foraging; Marine; Salt marshes; Species; Wading birds; Waterfowl; Wetland ecology; Wildlife habitats
• ISSN: 0738-6028
• DOI: 10.2307/1521355

In southern New Jersey, mixed-species foraging aggregations of wading birds occurred daily on salt marsh pools where they exploited dense fish populations. The species observed, in order of abundance, were the Snowy Egret (Egretta thula), Laughing Gull (Larus atricilla), Great Egret (Casmerodius alba), Glossy Ibis (Plegadis falcinellus), Forster's Tern (Sterna Forsteri), Common Tern (S. hirundo), Little Blue Heron (Egretta caerulea), and Tricolored Heron (E. tricolor). Aggregations probably assembled around Snowy Egrets. Most individuals in aggregations occupied positions within pools similar to those used when foraging alone. Numbers of individuals declined over the duration of an aggregation, probably in response to diminishing prey populations. Mean aggregation size and species richness peaked in late July and early August and declined significantly by September in response to recruitment of young, post-breeding dispersal, and migration, respectively. The proportion of most species within aggregations remained relatively constant over the duration of an aggregation and on a monthly basis. Other studies in temperate, subtropical, and tropical habitats also reported formation of aggregations around white-plumaged birds and periodic replenishment of prey populations.