A Historical Estimate of Apparent Survival of American Oystercatcher (Haematopus palliatus) in Virginia
Author(s): Erica Nol , Sean P. Murphy and Michael D. CadmanSource: Waterbirds, 35(4):631-635. 2012. Published By: The Waterbird Society
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BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofitpublishers, academic institutions, research libraries, and research funders in the common goal of maximizing access tocritical research. A Historical Estimate of Apparent Survival of American Oystercatcher (Haematopus palliatus) in Virginia
ERICA NOL1,*, SEAN P. MURPHY2 AND MICHAEL D. CADMAN3
1Biology Department, Trent University, Peterborough, ON, K9J 7B8, Canada
2U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, Corvallis, OR, 97331, USA
3Environment Canada, Canadian Wildlife Service, 867 Lakeshore Road, Burlington, ON L7R 5A6, Canada
*Corresponding author; E-mail: enol@trentu.ca
Abstract.—Using mark-recapture models, apparent survival was estimated from older banding and re-sighting
data (1978-1983) of American Oystercatchers (Haematopus palliatus) nesting on beaches and in salt marshes of coastal Virginia, USA. Oystercatchers nesting in salt marshes exhibited higher apparent survival (0.94 ± 0.03) than birds nesting on beaches (0.81 ± 0.06), a difference due to variation in mortality, permanent emigration, or both. Nesting on exposed barrier beaches may subject adults and young to higher risk of predation. These early estimates of adult survival for a species that is heavily monitored along the Atlantic and Gulf Coasts can be used to (1) develop demographic models to determine population stability, (2) compare with estimates of adult survival from popula-tions that have reached carrying capacity, and (3) compare with estimates of survival from other oystercatcher populations and species. Received 24 February 2012, accepted 17 July 2012.Key words.—American Oystercatcher, apparent survival, Haematopus palliatus, mark-recapture, shorebirds, Virginia.
The American Oystercatcher (Haemato-et al. 2005). In many states numbers of birds
pus palliatus), a Species of High Concern in nesting on beaches has declined, possibly the eastern United States (Brown et al. 2001), due to human disturbance (McGowan and has an estimated Atlantic Coast population of Simons 2006; Sabine et al. 2008), while num-10,971 ± 298 individuals (Brown et al. 2005). bers of birds nesting in salt marshes and shell Survival estimates of banded individuals are rakes have increased, comprising the major-critical to the development of demographic ity of nesting pairs in eastern North America models (Hitchcock and Gratto-Trevor 1997) (Lauro and Burger 1989; Wilke et al. 2005; that can be used to determine trajectories of lo-
Virzi 2010). Herein, we present a survival es-
cal or regional populations. Survival estimates timate of the American Oystercatcher from of marked individuals in the past are rare but a Virginia study population that was derived comparisons across historical timeframes can from a banded breeding population from also help to inform and assess management ac-
1978-1983 nesting on coastal beaches and salt
tions and future risks, especially in long-lived marshes in Virginia. organisms (De La Mare and Kerry 1994; Beiss-inger and Westphal 1998).
small in numbers relative to other North
From 1978 to 1983, field work was conducted from
American shorebirds, has re-colonized from March through July in salt marshes and beaches to the near extirpation (Mawhinney et al. 1999), and
south of Chincoteague, VA, (37° 50’ N, 75° 35’ W; Nol
increased over the last 50 years in the north-
et al. 1984). From 1978 to 1981, breeding adult oyster-catchers were captured during the incubation period
ern part of its range, reaching over 800 birds using drop traps placed over the nest (Mills and Ryder
in the states of Massachusetts and New York 1979). Birds were banded with a federal aluminum band (Melvin 2007; New York State Department of and a unique combination of 2-3 spiral color bands on Environmental Conservation). During this the tarsometatarsus. Observations of color-banded oys-recovery period, populations appear to be tercatchers were conducted over the breeding seasons
of 1979 to 1983. Sex of each bird was determined by size
declining in the core, Mid-Atlantic breeding and weight with females both larger and heavier (Nol
areas including Virginia and South Carolina et al. 1984). The study area and survey effort remained (Davis et al. 2001; Sanders et al. 2008; Wilke constant over the study period.
We used Cormack-Jolly-Seber (CJS, Cormack 1964;
Jolly 1965; Seber 1965) models using Program Mark 6.0 (White and Burnham 1999) to estimate apparent surviv-
We uniquely marked 58 (31 in 1978; twelve
al () and encounter probability (p) from live encounter
in 1979; four in 1980; eleven in 1981) nesting
data. This open population model assumes: 1) capture has no effect on survival or encounter probability; 2)
every oystercatcher has an equal chance of survival; 3)
nesting females, 13 beach-nesting females,
color bands are not lost; 4) capture periods are instanta-
17 marsh-nesting males, twelve beach-nesting
neous relative to the intervals between them; 5) fates are
independent, and 6) emigration is permanent (White
unique live encounters from 1979-1983. Us-
and Burnham 1999). Observations during this study sup-port these assumptions. To reduce the risk of violating
assumption 4, capture periods were held constant (15
April-15 June) over the study period. Apparent survival is
live encounter data (Ȑ = 1.57), adjusted AICc
the product of true survival and site fidelity and, as a re-
(QAIC ) by dividing the observed deviance
sult, is negatively biased. We included time-dependence
of the global model by the mean expected
(t) and sex (sex) in our models of and p because both parameters are known to vary between sex and across
deviance, and proceeded with model selec-
years in several shorebird species (Sandercock 2003).
Because habitat is also known to impact survival (Van de
our analysis included apparent survival as a
Pol et al. 2006), nesting habitat (habitat) was grouped into
function of nesting habitat and detection that
We assessed the fit of competing models using an
information-theoretic approach (Burnham and Ander-
the only other candidate model within two 6
son 2002). Selection of the best-fit model was done using
QAIC units, included an effect of habitat on
corrected quasi-Akaike’s Information Criterion adjusted
apparent survival and retained a time- and
for small sample size (QAIC , Lebreton et al. 1992). We
considered all models less than two QAIC units from
This model differed by only a single parame-
the model that minimized QAIC . We ranked models by
6QAIC and included normalized Akaike weights (w ).
ter, so does not improve model fit (Burnham
We conducted a goodness-of-fit (GOF) test for the global
and Anderson 2002; Arnold 2010). Apparent
strap procedure (White and Burnham 1999). The boot-
nesting on Virginia beaches was 0.81 (95%
strap GOF test compares the observed deviance to 1,000
CI: 0.67-0.90), whereas adults nesting in salt
randomly-generated replications, detects overdispersion in the data, and estimates a variation inflation factor, Ȑ,
marshes exhibited higher apparent survival
which corrects the data (Cooch and White 2009).
The Web of ScienceTM and unpublished sources are
probability (p) was high but varied annually
used to extract other estimates of adult survival for oys-
Table 1. Cormack-Jolly-Seber candidate models we used to estimate apparent survival () and recapture probabil- ity (p) for American Oystercatchers in Virginia, USA, 1978-1983. Quasi-Akaike’s Information Criterion for small sample sizes (QAIC ), differences in QAIC values (6QAIC ), normalized model weight (w ), model likelihood, i number of parameters (K), and deviance (Dev) are provided.
aModel factors included: habitat = nesting in barrier beach or marsh habitat, t = annual variation, c = constant, and sex = male or female. Table 2. Estimates of apparent survival for Ameri-
tat effects on survival, breeding-site fidelity
can Oystercatchers nesting on beaches ( ) and salt beach
or a combination of these two life-history
marshes ( ), encounter probabilities (p), standard marsh error (SE), lower 95% confidence limit (LCL), and up- per 95% confidence limit (UCL) in Virginia from 1978- 1983 under the best fit model ( , p ). habitat t
ing habitats, then the discrepancy between
apparent survival rates is a function of site fidelity varying by habitat. Using breeding
and nonbreeding encounters of oystercatch-
ers in Massachusetts, Murphy (2010) disen-
tangled site fidelity from survival and pro-
posed that local population swings are likely
the result of birds emigrating from the study population. Congeneric oystercatchers ex-
hibited higher levels of site fidelity to territo-ries that successfully fledged young (Safriel
etal. 1984; Ens et al. 1992; Harris and Wan-
terized as having high survival (Table 3) less 1997; Hazlitt and Butler 2001). Higher and breeding-site fidelity (Tomkins 1954; apparent survival of Virginia salt-marsh Hockey 1996). Thus, apparent survival of nesting oystercatchers may indicate higher adult oystercatchers is a credible estimate, reproductive output relative to those nest-and similar to that reported for American ing on beaches, as beach-nesting American Oystercatchers in Massachusetts (Murphy Oystercatchers experience both high mam-2010). The Virginia population was at a malian predation and human disturbance in much lower breeding density than the Mas-
other parts of their range (McGowan et al.
sachusetts population (Lauro et al. 1992; 2005; Sabine et al. 2008). Birds on beaches Murphy 2010), so density, at least, with this may have moved into nearby salt marshes limited sample, does not appear to impact (Wasilco 2008) or northward to growing adult survival. Our final model did not in-
clude the variable sex, a result that contrasts
Alternatively, equal levels of nest-site fidel-
with those for the similar Eurasian Oyster-
ity suggest a difference in survival between
catcher (H. ostralegus, Durell 2007). By con-
habitats with beach-nesting oystercatchers
trast, our final model suggested that adult experiencing direct mortality. At the time survival was 13% greater for birds nesting of the study, one inlet between two barrier in salt marsh habitat than for those nesting islands used for nesting was closing by move-on coastal beaches. As apparent survival es-
ment of sand, reducing saltwater flow to
timates are the product of true survival and oystercatcher feeding areas. Reductions in the probability that an individual returns to food supply could have contributed to lower the breeding site (i.e. breeding site-fidelity), apparent survival of beach-nesting birds. Ad-these differences may be attributed to habi-
ditionally, Red Foxes (Vulpes vulpes) denned
Table 3. Estimated adult survival (SE) of oystercatcher species (Haematopodidae).
1True survival; all others are apparent survival.
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