Abundance and distribution of birds from comprehensive surveys of the Canadian Arctic, 1994-2018

Abundance and distribution are critical metrics of population status and
foundational information for conservation. However, even these basic
metrics have been difficult to obtain for birds in the Canadian Arctic,
where costs are high and access is difficult. Here, we present estimates
of population size and distribution for 24 species of shorebirds and 37
other species of birds across the Canadian Arctic, using ground-based
surveys of 2,528 plots surveyed between 1994 and 2018. Plot locations were
selected by stratified random sampling, within wet, moist, or dry habitat
categories defined based on satellite remote sensing. Double-sampling was
used to determine detection rates and correct the estimates to reflect
birds breeding within the plots. Because this was the first large-scale
survey effort across Arctic Canada, many of the results provide new
insights with conservation implications. Nearly all estimated population
sizes for shorebird species exceed prior estimates, many by several-fold.
The six most abundant shorebird species were Calidris pusilla
(Semipalmated Sandpiper), Phalaropus fulicarius (Red Phalarope), Calidris
fuscicollis (White-rumped Sandpiper), Calidris melanotos (Pectoral
Sandpiper), Pluvialis dominica (American Golden-Plover), and Phalaropus
lobatus (Red-necked Phalarope), all with estimated population sizes
exceeding 3 million (CVs for these species ranged from 0.12 to 0.24).
Although shorebird densities were much higher in wet and moist habitats,
the large areal extent of dry habitats meant that 42% of all shorebirds
were estimated to occupy these dry areas, previously considered to be of
marginal importance. The estimates of abundance and distribution for the
37 non-shorebird species are, in many cases, the first ever estimates of
population size from the Arctic breeding grounds. This new understanding
of population sizes will have important implications for several current
conservation programs, such as those where areas are identified as key
habitat on the basis of the percentage of populations using them.