Effectiveness of Call-Broadcast Surveys for Breeding Marsh Birds Along Coastal Alabama

Abstract

Point-count surveys targeting Ixobrychus exilis (Least Bittern), Laterallus jamaicensis (Black Rail), Rallus longirostris (Clapper Rail), Rallus elegans (King Rail), Porphyrio martinica (Purple Gallinule), and Gallinula chloropus (Common Moorhen) were performed using a standardized marsh-bird monitoring protocol along tidally influenced emergent marshes of coastal Alabama during the 2004 breeding season. We compared the number of target species detected during an initial passive-listening period to those detected during a subsequent multiple-species call-broadcast period to evaluate the effectiveness of the call-broadcast period for increasing detections. Additionally, we examined the number of responses of each target species to conspecific and heterospecific calls to determine how marsh birds respond to multiple species call-broadcast sequences. Numbers of new individuals detected during call-broadcast periods were significantly greater (P < 0.05) than those detected during the initial passive-listening period for Clapper Rail, King Rail, and Purple Gallinule, but not for Least Bittern and Common Moorhen. Black Rails were not detected during this study. Conspecific calls were more effective at eliciting responses than heterospecific calls for each of the target species except Least Bittern. Although the calls of Clapper Rail and King Rail are very similar, our data indicate that the advertisement calls of both species should be incorporated within multiple species call-broadcast sequences where populations are sympatric. We also recommend that Purple Gallinule call-broadcasts be applied to marsh-bird inventories or monitoring programs throughout this species' range as a result of its effectiveness, which was previously uncertain.