Kelsi L. Hunt

The importance of site to mate choice: Mate and site fidelity in Piping Plovers

ABSTRACT Each breeding season, seasonally monogamous birds can divorce or reunite with their previous years mate, assuming both partners survive and return. We tested a suite of variables related to mate choice and site choice to determine which of 4 prominent mate fidelity hypotheses (better [mate] option, habitat mediated, musical chairs, and bet-hedging) best explained the interyear reunion rate and breeding dispersal of a seasonally monogamous shorebird, Piping Plover (Charadrius melodus), nesting on dynamic sandbars on the Missouri River, USA, 2005–2012. Of 252 pairs in which both members returned to the breeding grounds the following year, only 20% reunited. Pairs with an early-arriving male had the highest mate fidelity. Reunited pairs returned to previous nest sites (median breeding dispersal = 39 m), and divorced and widowed birds tended to move farther (median = 229 m and 193 m, respectively). Overall, site fidelity was higher in males than females. Previous reproductive success of a pair did not predict reunion, but all successful birds, with the exception of divorced females, exhibited high site fidelity, suggesting selection for site based on prior breeding success. Among divorced birds, females had higher-quality mates and higher nest success compared to their former partners, and they nested in areas of similar quality between years, whereas males settled in lower-quality areas following divorce. The benefits that females gained from divorce suggested that females initiated divorce to improve reproductive success, which supports the better option hypothesis. Although females seemed to initiate most divorces, males may have divorced as a safeguard against remaining unmated when there was uncertainty about the survival and return of a former mate, as proposed by the bet-hedging hypothesis.

Density Dependent Double Brooding in Piping Plovers (Charadrius melodus) in the Northern Great Plains, USA

Abstract. Piping Plovers (Charadrius melodus) are primarily monogamous birds that usually raise only one brood per season, but rare instances of double brooding have been documented. Piping Plovers breeding in the northern Great Plains, USA were studied in two locations: the Missouri River near the Gavins Point Dam (2005– 2013) and the lower Platte River (2008–2013). There were 25 confirmed instances of double brooding on the Missouri River across the 9-year duration of the study. There were no instances of double brooding observed locally on the lower Platte River. However, in 2013, two female Piping Plovers successfully hatched eggs and fledged chicks from nests on the lower Platte River and later were observed nesting for a second time on the Missouri River. Factors predicted to increase the frequency of double brooding are: early nest initiation, male biased sex ratio, age of breeding adults, and decreased nesting density. Our results indicate density is an important factor that accounts for some of the difference in the proportion of double brooding on the Missouri River compared to the lower Platte River. It is likely a combination of factors is responsible for this behavior, previously thought to be rare, in Piping Plovers.

Hatch-year Piping Plover (Charadrius melodus) prospecting and habitat quality influence second-year nest site selection

ABSTRACT Juvenile prospecting, or exploratory behavior for gleaning information about areas or events, can have profound effects on the selection of future breeding habitat, particularly for birds with high site fidelity whose initial choice of breeding habitat could represent a lifetime investment in fitness. We present data from a 10-yr study of Piping Plovers (Charadrius melodus) on the Missouri River, USA, to determine whether postfledging, hatch-year (HY) prospecting movements inform second-year (SY) nest site choices. First, we compared the home ranges of HY and adult (after-hatch-year; AHY) plovers to investigate whether differences in habitat use existed between HY and AHY plovers. Second, we evaluated the effects of prospecting, nest density, reproductive success, and nesting and foraging habitat availability on SY plover nest site selection. Lastly, we evaluated the potential reproductive benefits of nesting in prospected areas by comparing the nest success and fledging success of SY plovers that nested within their HY prospecting range with the success of those that nested in presumably unexplored areas. Plover home ranges varied across ages and among years. Both HY and AHY plover home ranges were smaller when the proportion of foraging habitat in the home range was relatively high, compared with nonforaging habitat. Second-year plovers selected sandbars that they had prospected as HY birds more often than would have been expected if nest site selection were random. Second-year plovers also selected sandbars on which other plovers experienced higher average nesting success than on random nesting locations, but we found no evidence that individual SY birds that nested on prospected sandbars had higher reproductive success than individuals that nested in unexplored areas. Coupled with high adult site fidelity, affinity of plovers for sandbars where they experience relatively high average reproductive success could lead to long-term gains in fitness.

Senescence and carryover effects of reproductive performance influence migration, condition, and breeding propensity in a small shorebird

Abstract Breeding propensity, the probability that an animal will attempt to breed each year, is perhaps the least understood demographic process influencing annual fecundity. Breeding propensity is ecologically complex, as associations among a variety of intrinsic and extrinsic factors may interact to affect an animals breeding decisions. Individuals that opt not to breed can be more difficult to detect than breeders, which can (1) lead to difficulty in estimation of breeding propensity, and (2) bias other demographic parameters. We studied the effects of sex, age, and population reproductive success on the survival and breeding propensity of a migratory shorebird, the piping plover (Charadrius melodus), nesting on the Missouri River. We used a robust design Barker model to estimate true survival and breeding propensity and found survival decreased as birds aged and did so more quickly for males than females. Monthly survival during the breeding season was lower than during migration or the nonbreeding season. Males were less likely to skip breeding (range: 1–17%) than females (range: 3–26%; βsex = −0.21, 95% CI: −0.38 to −0.21), and both sexes were less likely to return to the breeding grounds following a year of high reproductive success. Birds that returned in a year following relatively high population‐wide reproductive output were in poorer condition than following a year with lower reproductive output. Younger adult birds and females were more likely to migrate from the breeding area earlier than older birds and males; however, all birds stayed on the breeding grounds longer when nest survival was low, presumably because of renesting attempts. Piping plovers used a variety of environmental and demographic cues to inform their reproduction, employing strategies that could maximize fitness on average. Our results support the “disposable soma” theory of aging and follow with predictions from life history theory, exhibiting the intimate connections among the core ecological concepts of senescence, carryover effects, and life history.

Impacts of anthropogenic disturbance on body condition, survival, and site fidelity of nonbreeding Piping Plovers

ABSTRACT The impact of habitat loss on shorebirds may be exacerbated by disturbance from human recreational use, which further reduces the amount of coastal habitat that is functionally available. This can have consequences for the condition of individual birds or for population processes, both of which should be considered in strategies to reduce conflict between shorebirds and recreational users of coastal habitat. Our objectives were to determine the associations between human recreational use, coastal habitat modifications, and Piping Plover (Charadrius melodus) body condition and demography. We monitored banded Piping Plovers throughout their annual cycle to assess variation in body condition, true survival, and site fidelity related to disturbance regimes in 8 geographically proximate, nonbreeding areas along the southeastern Atlantic Coast of North America from 2012 to 2016. Piping Plovers in disturbed sites were 7% lighter than those in less disturbed sites. Additionally, true annual survival was lower in more disturbed areas. However, site fidelity was less influenced by disturbance than were body mass and survival. Movements away from specific nonbreeding areas were uncommon, regardless of disturbance regime, but individuals that moved to new wintering locations had high probabilities of annual survival (S̄ = 0.80) relative to their site-faithful counterparts (S̄ = 0.67). Associations among nonbreeding conditions, body condition, and demography highlight the importance of nonbreeding habitats to annual population dynamics of migratory species. Conservation strategies for Piping Plovers that focus solely on breeding season dynamics may not account for some of the mechanisms that influence demographic rates and population trajectories.

Demographic response of Piping Plovers suggests that engineered habitat restoration is no match for natural riverine processes

ABSTRACT Globally, riparian ecosystems are in decline due to anthropogenic modifications, including damming. Reduced frequency and altered timing of flood events decreases sandbar deposition, which reduces habitat for sandbar-breeding birds, including the threatened Piping Plover (Charadrius melodus). In response to limited breeding habitat and small populations, the U.S. Army Corps of Engineers constructed 255 ha of sandbar habitat on the Missouri River, USA, from 2004 to 2009. During the breeding seasons of 2010 and 2011, historically high flows resulted in the creation of 1,046 ha of suitable sandbar habitat on the Missouri River. We compared the demographic responses of Piping Plovers to this anthropogenic and natural habitat creation. We found that demographic parameters, including nest success (x̄preflood = 0.45 ± 0.02 SE vs. x̄postflood = 0.74 ± 0.02 SE), prefledging chick survival (x̄preflood = 0.39 ± 0.09 SE vs. x̄postflood = 0.65 ± 0.03 SE), and hatch-year survival (x̄preflood = 0.16 ± 0.03 SE vs. x̄postflood = 0.46 ± 0.03 SE), were consistently higher on the flood-created habitat than on the engineered habitat, leading to population growth after the flood. These differences were related to increased sandbar habitat, low nesting densities, and decreased nest and chick predation. As ecosystems are increasingly altered, ecologists seldom have the opportunity to make appropriate comparisons between managed and natural ecosystem processes. Our results suggest that management intervention may not be an appropriate substitute for natural ecosystem processes in riparian ecosystems.

Least Tern (Sternula antillarum) nest success and chick survival on the Missouri River following historic flooding

ABSTRACT On the Missouri River, the federally endangered interior population of Least Terns (Sternula antillarum) historically nested on sandbars created by sediment deposited during high flows. The Missouri River has been dammed and regulated, however, resulting in decreased flooding and sediment deposition and thus decreased sandbar habitat. In 2011, unusually high water releases created extensive sandbar habitat on the Gavins Point Reach of the Missouri River, and from 2012 to 2014 we examined the post-flood demography of Least Terns. We monitored 382 nests, uniquely marked 672 chicks, and attempted to recapture chicks every 3–4 d until fledging (∼18 d). Daily nest survival was high (0.99 [SE 0.002]), resulting in high mean nest success (0.87 [0.03]). Nest success was highest in 2012 and declined slightly each year. Daily chick survival was 0.96 (0.01), resulting in a mean survival to fledge of 0.44 (0.08). Daily chick survival did not vary by year or by age of chicks but was negatively correlated to hatch date. Similar to another sandbar nesting species, the federally threatened Piping Plover (Charadrius melodus), Least Terns were highly productive on sandbars created by flooding on the Gavins Point Reach of the Missouri River. Least Terns may have taken advantage of newly created sandbars with similarly high reproductive output to boost and maintain population levels.