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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

Methodology -- Section B


Nest finding

Abilities of investigators to locate piping plover nests on alkali beaches vary considerably and do not always relate to experience level.

Nests usually can be found during censuses, although at areas of concentrated breeding (>5 pairs/km²) it may be most practical to nest-search after completing a census. Plovers are not as attentive to their nests during laying, which adds difficulty to early nest searches.

Nesting plovers seem most attentive in relatively cool weather (<20 C [70 F]), and investigators probably can search for nests in temperatures to 13 C (55 F) without threatening embryo viability (S. Haig and C. Kruse, pers comm); hot weather (>29 C [>85 F]) likely poses greater risk

Concentrating on a search image is helpful while trying to pinpoint nests close up (i.e., visualizing the pale buff-colored eggs, or a ring of tiny stones that forms the nest bowl rim).

Plovers place nests on open gravel patches and avoid areas dominated by mud, heavy cobbles, or dense vegetation (Whyte 1985, Prindiville Gaines and Ryan 1988), although there always are exceptions.

Nest finding is facilitated by behavioral cues. Through mid-incubation (typically, late May through mid-June), plovers dash from nests in a low, silent run when an investigator comes within 20-60 m. They may remain on nests longer during late incubation or when air temperatures are cool.

The direct run appears furtive, with the head lowered, and is followed by nervous head pumping and perhaps a few alarm notes when the plover is 20-30 m from the nest. While walking slowly along the beach, the investigator should scan far ahead for this behavior and then carefully trace backward along the line of departure to find a nest.

If a plover appears to already have left its nest, the investigator can sit or lie down 10-15 min in uplands and observe, then stand up while scanning for plovers moving from nests. This technique is especially useful on beaches lacking vantage points but, again, will not work as well in hot weather.

An obvious behavior of adult plovers associated with nests (and chicks) is distraction display (especially the "broken wing display") to lure intruders away. Nesting plovers use such displays mainly within 2 wk of hatching; display intensity generally increases as hatching nears (Cairns 1982).

False incubation (false brooding) is another common distraction behavior: Adults suddenly stop and squat, appearing to have settled on eggs.

Whenever such strong distraction displays are observed, eggs (or chicks) are likely within 20-30 m. If a nest is not found within 2-3 min, the investigator probably should back away and end disturbance by observing quietly from a concealed vantage point.

Initially, investigators should try to combine searches for nests with censussing, starting at breeding sites with relatively few, isolated pairs. A slow walk, alternately approaching and backing away from the nesting beach while observing behavior and movements of adult plovers, may serve as the primary tool.

Other techniques for nest finding include remote observation, observation from a small boat, searching near old nest scrapes, and walking narrow transects through defended habitat. Descriptions of these follow.

Remote observation

Spotting scopes can be used to find incubating adults from up to 400 m away, particularly in morning when cool air temperatures minimize heat distortion in the scope view field and low light angles accent the silhouette and distinguishing plumage features of plovers on nests. The contrast of the dark forehead bar or neck band with the otherwise light plumage is particularly noticeable.

Elevated (>2 m) vantage points such as hilltops are helpful. In some situations it may be possible to view from a vehicle or even a step ladder (with a dark blanket or camouflage netting cover).

Plovers signal the approach of a predator with alarm calls, which may add opportunity to find nest. For example, incubating plovers usually respond to approaching northern harriers (Circus cyaneus) by darting from nests, and an adult that suddenly appears after the passing of a harrier can be expected to return to its nest within 5-10 min.

Focused attention on a lone adult guarding its territory usually leads to discovery of a nest within 1 hr, when the bird exchanges incubation duties with its mate.

An advantage to remote observation is the opportunity to find nests without disturbing breeding pairs. It is an excellent approach where topography or vegetation adjacent to the nesting beach impairs closer viewing, especially if there is concentrated nesting including American avocets.

A disadvantage is low efficiency (number of nests found/hour) especially if lighting is poor or beaches are neither relatively flat nor sparsely vegetated. Also, a nest's location must be noted with extra care when viewed from long distances because the site inevitably looks much different when viewed closely from a different angle. Simple nest site sketches, noting landmarks such as distinctively shaped or colored cobbles, can help.

A simple, effective version of remote observation is to have a second investigator walk to the beach edge so an incubating adult moves from its nest. The investigator returns to observe from a remote vantage point with the first investigator. Then, each investigator watches an opposite member of a breeding pair until either adult returns to the nest. This can be done by one investigator, but not as effectively.

Boats

Observation from a small boat 30-50 m off shore is a specialized form of remote observation.

Under certain conditions, it is a superior technique for finding and monitoring nests, as well as for counting chicks and fledglings. Nests can be found two to three times faster from a boat than by other techniques (R. Murphy and K. Smith, pers obs), with almost no apparent disturbance to nesting plovers. Indeed, plovers do not seem to recognize a person in a boat as a threat, although American avocets, which often share breeding habitat with piping plovers, exhibit at least mild defense behavior.

It generally is inefficient to use boats where breeding pairs of plovers are sparsely distributed (e.g., 1 pair/km of shore). Some alkali lakes are too shallow to draft even a flat-bottomed johnboat or quickly become so after only a week of strong wind and high temperatures. Observation is difficult in even moderate winds, and boat access may be unavailable at some breeding sites.

When using small boats for nest searching and subsequent reproductive monitoring, investigators should (1) stay at least 30 m from shore, (2) row and move slowly and quietly, and (3) not disembark or stand in the boat when within 100 m of beaches.

If an investigator lands a boat on a nesting beach or steps out and walks ashore (e.g., to pinpoint a nest), plovers will on subsequent visits consider the boat a threat and utter alarm notes, and nests or chicks will be difficult to observe. Investigators should either map locations of nests, or should communicate with a second observer onshore by hand-held radio.

To minimize problems with wind, boats should be used in early morning, starting at sunrise. Temperature and lighting also tend to be conducive to nest-finding at that time. Additional recommendations may be found in J, Equipment.

Searching near old nest scrapes

Piping plovers tend to be strongly faithful to breeding territories year after year (Haig and Oring 1988). The authors sometimes find them nesting close to or even in the previous year's nest and thus discover some nests quickly by initiating a search at an old site. The technique depends on familiarity with a particular beach and its old nest markers or on detailed breeding site maps.

Walking narrow transects through defended habitat

The authors do not advocate this approach because it presents unreasonable risk to nests (i.e., from being stepped on) and, likely, prolonged (>15 min) disturbance.

It should only be considered by those with excellent ability to find nests close up, and only where all other nest-searching methods fail, but even experienced investigators have difficulty finding nests with this method.

By walking slowly (1-2 kmph [about 1 mph]) and systematically scanning virtually every cm² within 1-2 m, an experienced investigator can find nests especially on beaches with concentrated nesting.

Along narrow, parallel transects, the investigator traverses a section of beach where nesting is suspected. Cobbles should be used as "stepping stones" where available to avoid stepping on eggs or chicks. Two persons can work in tandem with a zone of overlap between them. Behavior of nearby adult plovers and recent scrapes may help narrow the search.


Previous Section -- Section A - Censuses of breeding plovers
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Next Section -- Section C - Marking nests

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