Aggressive Behavior in Male Black Skimmers

Black Skimmers (Rynchops niger) are an imperiled colonial-nesting seabird who breed in the summer. During the breeding season, Black Skimmer pairs defend small territories from encroachment by other adult Black Skimmers. Therefore, we asked how often specific aggressive behaviors are directed towards conspecifics. From June to August 2023, we observed banded male Black Skimmers at two nesting colonies: St. Pete Beach and Redington Shores in Pinellas County, Florida. We conducted both morning and evening ten minute all-occurrence focal observations (n = 423). In an observation session, a single individual was observed and every instance of aggressive behavior was recorded. We recorded seven aggressive behaviors: aerial chase, aggressive upright, bark, ground chase, head toss, low oblique, and walk towards. We organized and calculated descriptive statistics using the software package R. Overall, barking was the most common aggressive behavior observed. Barking had the highest median rate (1.3 actions/minute), followed by head toss (0.2 actions/min), and aggressive upright (0.1 actions/min). High barking rates may indicate that barking is a low-energy behavior and an effective way to respond to threats. Despite their conservation status, Black Skimmers are not well-studied and any information on their activity during breeding is beneficial for management decisions. 

For more information: jhughes@eckerd.edu

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