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Piping Plovers and Least Terns of
the Great Plains and Nearby

A draft protocol for assessing piping plover reproductive success
on Great Plains alkali lakes


breeding (or nesting) density:
number of breeding pairs per unit area (usually, per km²); may be based on total wetland area or on arbitrary breeding site boundaries such as section or quarter-section lines that might encompass some upland habitat.
breeding pair:
two adult piping plovers that exhibit bonding through sexual behavior, defend a breeding territory for >2 wk against other adult plovers, and have a scrape that is at least one third lined with tiny pebbles. A lone adult plover on a nest or with chicks also is considered a breeding pair, whereas an otherwise lone, territorial adult, such as a male doing courtship flights, is not. During an annual population census or similar count, what appear to be breeding pairs may be labeled simply as "pairs" in lieu of more specific evidence.
breeding site:
usually an individual alkali lake, but sometimes a complex of lakes and ponds in close proximity (<1 km apart) or a discrete part of a large (>5 km²) lake, where plover breeding has been recorded. The site is usually identified in state, provincial, and other databases by a consistently used name (e.g., Big Quill Lake, Lake Williams).
breeding territory:
area defended by a breeding pair of plovers, size highly variable, e.g., average 27,000-31,000 m² at Big Quill Lake, Saskatchewan (Whyte 1985), to 500 m² at relatively high local densities at Williams Preserve in central North Dakota (B. Root, unpubl data); changes through breeding season.
chick success:
proportion of hatched eggs that produce fledglings (if Mayfield chick success, either each chick or each brood of chicks is the sampling unit interest; see I, Reporting measures of reproductive success).
egg success:
proportion of eggs that hatch.
exposure days:
time (days) that a clutch of eggs under observation is vulnerable to loss (e.g., from predation or weather).
fledgling or fledged chicks:
technically, juvenile plovers capable of sustained (>15 m) flight, which on alkali lakes first occurs at 21-28 days (Pridiville Gaines and Ryan 1988). To minimize methodological biases when assessing reproductive success (see D, Nesting chronology: initiation, hatching, and fledging dates), defined here as juveniles 18-20 days old.
fledging rate:
estimate of the mean number of flighted juveniles produced per breeding pair, based on total numbers of breeding pairs and 18- to 20-day-old chicks observed.
nest or nesting attempt:
a scrape that has ≥1 egg.
nest success:
proportion of nests that result in ≥1 hatched egg.
nonterritorial adult(s):
adult plovers that exhibit little or no territorial defense or evidence of pairbonding and that vocalize infrequently, such as at feeding sites such as spring seeps on alkali lakes.
pair success:
proportion of breeding pairs that successfully hatch eggs (Smith et al. 1993) or fledge young (must specify), regardless of number of attempts.
reproductive success (or productivity):
general term for measures of fecundity; in birds, refers either to the quantity of (1) eggs, (2) nests with hatched eggs, (3) chicks, or (4) fledged young, whether based on total numbers of pairs, females, breeding-age adults, or successfully breeding birds. For piping plovers, fledging rate based on total breeding pairs is the most important and least biased measure of reproductive success.
depression dug mostly by male as part of courtship display. Several scrapes may be made within a breeding territory, but only one is selected for a nest site.

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