Point count summary statistics differentially predict reproductive activity in bird-habitat relationship studies

Abstract

Point count summary statistics (e.g. mean abundance, maximum abundance, frequency and presence/ absence) reflect different assumptions about behavioral and population processes. In this paper we (1) determine the frequency and usage trends of different point count summary statistics in recent ornithological literature, and (2) assess how well point count data, summarized using five common statistics, predict an alternate measure of habitat quality-reproductive activity. For the 100 journal years we reviewed (10 journals over 10 years), 148 papers used point counts to evaluate bird habitat relationships. The number of papers using point counts has increased over the decade. Mean abundance, the most common summary statistic, was used more than twice as frequently as the next most common summary statistics. Only 25.7% (38 papers) provided a justification for use of a particular summary technique. We conducted point counts in three Canadian study regions (New Brunswick, Nova Scotia, and Newfoundland and Labrador) comprised of two ecosystem types (forest and grassland). While there was a statistically significant positive correlation between point count data and reproductive activity data for most species, we found that point counts were often unsuccessful at predicting reproductive activity in forest birds. For species where point counts adequately predicted reproductive activity mean abundance and frequency were consistently the best predictors. Our results indicate that statistics using information on intra-season (multiple-visit) occupancy tend to be better estimators of reproductive activity.

Bobolink reproductive response to three hayfield management regimens in southern Ontario

“…Reproductive activity was classified for each point count station over the season by assigning an ordinal index rank, progressing from 0 when no bobolinks were settled on-site, 1 for male presence >3 weeks, 2 for female presence >3 weeks, 3 for evidence of pairing (such as females carrying nest materials), 4 for adults carrying food to presumed nestlings, and 5 for observed fledglings. This method is useful to examine differences in the overall reproductive activity achieved between management regimens, rather than to estimate the timing of phenological events (Betts et al 2005). In 2011, field searches were conducted every 3-5 days on early managed fields after first harvest to detect bobolink (re)colonization and reproductive activity.…”

Bird communities and vegetation associations across a treeline ecotone in the Mealy Mountains, Labrador, which is an understudied part of the boreal forest

“…Abundance was calculated by taking the mean number of individuals of each species for each visit (Betts et al 2005).…”

Conservation Concern for the Deteriorating Geographical Range of the Grey Parrot in Cameroon

“…Point counts involve mainly visual and auditory detections of birds with fixed or unlimited radius plots [15,18]. Their efficiency and accuracy are influenced by observer effort, which may affect the information obtained such as species abundance [19][20][21]. If well spaced, a sample series of points in an area will provide more representative data than a few transects.…”