Copy of `USGS - Depredation of Duck Nests`

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USGS - Depredation of Duck Nests
Category: Animals and Nature
Date & country: 30/06/2013, US
Words: 22


Artificial nest
Depression scraped in soil and usually lined with nest material (to simulate the appearance of a natural nest) by an investigator in which eggs (always 6 in the present study) were placed by the investigator.

Chip of shell
Single detached piece of shell <1 cm diameter.

Depredated nest
Nest with ≥1 egg known depredated.

Displaced nest material
Nest material pulled or otherwise removed from a nest by a predator and located >5 cm outside the original nest edge established by the attendant hen or the investigator. Nest material >5 cm outside the original nest edge but connected to the nest is displaced. Nest material rearranged or matted in the nest is not displaced.

Eggshell
Single piece of shell or pieces of shell connected by membrane that represent >50% of the total shell of an egg.

Eggshell that has large hole
Eggshell with ≥1 opening and >50% but ≤75% of the original shape of the egg intact.

Eggshell that has small hole
Eggshell with ≥1 opening and >75% of the original shape of the egg intact.

Eggshell that is fractured
Eggshell with ≥1 opening and 25-50% of the original shape of the egg intact.

Eggshell with opening in a side-end
Eggshell with >50% of original shape of the egg intact in which the opening extended from the side into an end or there was an opening in the side and another in an end.

Eggshell with opening in an end
Eggshell with >50% of original shape of the egg intact in which all openings in the egg were in 1 or both ends of the egg.

Eggshell with opening in the side
Eggshell with >50% of original shape of the egg intact in which all openings in the egg were in the side of the egg.

Exposure-day
One nest at risk of depredation during all or part of a 24-h period.

Fragment of shell
Single detached piece of shell or connected pieces of shell that represent ≤50% of the shell of an intact egg. Shell chips are small shell fragments.

Loose egg(s)
Individual egg or small number of eggs placed on the ground surface to attract predators but with no attempt to simulate a clutch in a nest. All loose eggs offered to predators in this investigation were duck eggs.

Membrane of egg
Thin pliable lining separating the embryonic content of an egg from the outer calciferous shell.

Nest depredation record
The record of information describing evidence of depredation found at a nest destroyed by predators.

Nest success
The probability that ≥1 egg of a clutch hatches (Cowardin and Johnson 1979).

Offending predator
Individual predator that depredated or destroyed a nest.

Principal predator
One of 9 species and 2 groups of congeneric species with potential to destroy significant numbers of duck nests in the Prairie Pothole Region.

Puncture hole
Small hole (≤1 cm diameter) punctured through the shell and membrane of an egg by a predator but which is not the main opening in the eggshell.

Retreat
Site used by a mammalian predator for resting.

Verification data
Data describing nest depredations for which the offending predator species was known or presumed known.