Nest Site Selection of American Oystercatchers (Haematopus palliatus) on the Upper Texas Coast with Comments on Field Sexing Techniques

• Main Author: Munters, Alexandra E.
• Other Authors: Green, M. Clay, Simpson, Thomas R., Weckerly, Floyd
• Language: English
• Published: 2014
• Subjects: Oystercatcher; Habitat selection; Nest site selection; Spatial ecology; American oystercatcher; Nest building; Birds > Texas; Rookery Islands; Shell Island
• Online Access: https://digital.library.txstate.edu/handle/10877/4998

The American Oystercatcher, hereafter oystercatcher, is a shorebird species of high conservation concern that requires intertidal shellfish beds for breeding and wintering habitat. Considerable attention has been paid to obtaining site-specific productivity data and determining factors contributing to their reproductive success on the Atlantic coast; however no data exists for populations along the Texas coast. I monitored breeding oystercatchers on the upper Texas coast and discovered 58 and 83 nests during 2011 and 2012, respectively. During 2011 productivity was 0.78 based on 36 chicks fledging from 46 breeding pairs. During 2012, productivity was 0.21 based on 10 chicks fledging from 48 breeding pairs. Oystercatchers in Texas nested in 4 types locations: 52% of nests (n=74) were on emergent shell island, 37% (n=53) on the periphery of colonial waterbird rookery islands, 6% on shell spits connected to the mainland at low tide (n=8), and 5% on the mainland (n=7). The most common plants at oystercatcher nests on the Texas coast were sea purselane (Sesuvium portulacastrum), Carolina wolfberry (Lycium carolinianum), saltwort (Batis maritima), and sea ox eye daisy (Borrichia frutescens). I investigated nest site selection at two scales, microhabitat at the nest site and landscape scale at the presumed territory. I measured the same variables at nests and at randomly selected unused locations within the study area and then performed logistic regression to determine if oystercatchers were selecting nest locations non-randomly. Fifteen percent of nests surveyed were on shell substrate with no vegetation whereas overall, nests averaged 30% live vegetative cover. There was no significant difference between the amount of live vegetation (df= 147, r!<0.001, p=0.874) or shell (df= 147, r!=0.002, p=0.602) at nest locations and random locations. There was also no significant effect of the amount of vegetation (df= 73, r!=0.093, p=0.078) or shell (df= 73, r!=0.093, p=0.220) at nest locations on the likelihood of fledging. ...