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M.S. Thesis Defense - Elsa Forsberg

Demographic consequences of off-river nesting for piping plovers (Charadrius melodus) and interior least terns (Sternula antillarum athalassos) in the Lower Platte River system, Nebraska

9:30 am – 10:30 am
Hardin Hall Room: 901 South
3310 Holdrege St
Lincoln NE 68583
Additional Info: HARH
Virtual Location: Zoom Webinar
Target Audiences:
Mark Vrtiska,
Piping plovers (Charadrius melodus; hereafter plovers) and interior least terns (Sternula antillarum athalassos; hereafter terns) are two avian species that nest along the Lower Platte River system (LPRS) in Nebraska. Natural nesting habitat for both species consists of sparsely vegetated expanses of sand near water. In the LPRS, river sandbars provide natural nesting habitat for plovers and terns. Sandbar habitat has been reduced from historical availability due to anthropogenic modifications and annually variable depending on hydrological fluctuations. Plovers and terns in the LPRS also nest at off-river sites, such as sand and gravel mines and their derivatives, transition sites and lakeshore housing developments. Off-river sites provide most of nesting habitat in the LPRS when sandbar habitat is scarce and are presumed to be important for the persistence of plovers and terns in the LPRS. However, the quantity of plover and tern nesting habitat provided by off-river sites is not self-sustaining and predicted to decline due to changing sand and gravel mining industry practices. Understanding the vital rates of plovers and terns in the LPRS will inform the role that off-river sites hold in the future conservation and long-term persistence of both species. To contribute to this understanding, I assessed consequences of off-river nesting between sandbars and off-river sites and among off-river site types using a long-term monitoring database collected by the Tern and Plover Conservation Partnership from 2008-2023. I also investigated additional factors that could affect vital rates such as the timing of nest initiation and hatching, extreme temperatures, conspecific and heterospecific nesting proximity, and nest exclosure usage (plovers only). For plovers, I evaluated annual and intra-seasonal adult survival, annual hatch-year survival, pre-fledging chick survival, and pre-fledging chick growth rates at off-river sites, and nest survival at off-river sites and sandbars. For terns, I evaluated pre-fledging chick growth rates and nest survival at off-river sites and sandbars. I did not find evidence for a difference between off-river sites and sandbars in nest survival for either species or for tern chick growth. Among off-river sites, plover chick growth was greatest at housing sites and tern chick growth was greatest at mine sites. There was no evidence that hatch date affected growth of plover chicks, but later hatched tern chicks had greater growth. Nest survival for plovers did not differ among off-river sites but was greatest at housing sites for terns. For both species, nest survival increased with increasing proximity to tern nests, greater proportion of incubation days with ambient temperatures above mean high temperatures, increasing nest age, and decreasing nest initiation date. Exclosed plover nests had higher survival. There was no evidence to show a difference in survival for adult plovers with exclosed nests. Plover adult, hatch-year, and chick survival was comparable to estimates of other populations. These results demonstrate the dynamics of plovers and terns in the LPRS and the importance of off-river habitat for the persistence of plovers and terns in the LPRS. Specifically, the lack of evidence for a demographic consequence of off-river nesting to nest survival or tern chick growth suggests that off-river habitat may support plovers and terns similarly to river sandbars. Furthermore, prioritization of early season nests may be most efficient for conservation and management resources, however tern chicks may benefit from investment later in the breeding season. As nesting near terns may improve plover nest success, measures to protect terns may also benefit plovers. Additionally, continued use of nest exclosures may improve nest success for plovers with limited effects to adult survival. Continued monitoring and study of plovers and terns at off-river sites and sandbars, particularly in the face of changing climatic and industry conditions, will further support the persistence of these species in the LPRS.

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This event originated in SNR Seminars & Discussions.