Abstract
Monitoring Adélie penguin (Pygoscelis adeliae) populations on the Western Antarctic Peninsula (WAP) provides information about the health of the species and the WAP marine ecosystem itself. In January 2017, surveys of Adélie penguin colonies at Avian Island and Torgersen Island off the WAP were conducted via unoccupied aircraft systems (UAS) collecting optical Red Green Blue (RGB), thermal, and multispectral imagery. A semi-automated workflow to count individual penguins using a fusion of multispectral and thermal imagery was developed and combined into an ArcGIS workflow. This workflow isolates colonies using multispectral imagery and detects and counts individuals by thermal signatures. Two analysts conducted manual counts from synoptic RGB UAS imagery. The automated system deviated from analyst counts by −3.96% on Avian Island and by 17.83% on Torgersen Island. However, colony-by-colony comparisons revealed that the greatest deviations occurred at larger colonies. Matched pairs analysis revealed no significant differences between automated and manual counts at both locations (p > 0.31) and linear regressions of colony sizes from both methods revealed significant positive relationships approaching unity (p < 0.0002. R2 = 0.91). These results indicate that combining UAS surveys with sensor fusion techniques and semi-automated workflows provide efficient and accurate methods for monitoring seabird colonies in remote environments.
Highlights
For wildlife biologists, occupied aircraft surveys are crucial tools that inform both ecological studies and conservation decisions by providing critical information on the status and trajectories of vertebrate animal populations, including assessments of colonial seabirds [1,2]
An early study showed that using kites to take pictures of breeding colonies along the Western Antarctic Peninsula could be a more cost-efficient method to count Adélie penguin populations, especially for large colonies [5]
To identify individual penguin colonies, we examined near infrared (NIR) or Normalized Difference Vegetation Index (NDVI) reflectance values of known guano patches throughout the image to define a threshold value that captured the lower limit of guano reflectance values
Summary
For wildlife biologists, occupied aircraft surveys are crucial tools that inform both ecological studies and conservation decisions by providing critical information on the status and trajectories of vertebrate animal populations, including assessments of colonial seabirds [1,2]. An early study showed that using kites to take pictures of breeding colonies along the Western Antarctic Peninsula could be a more cost-efficient method to count Adélie penguin populations, especially for large colonies [5]. Others have developed methods for aerial imagery using methods such as semi-automated thresholding [25], and image segmentation [4] Most of these studies focused on detecting and quantifying the area of penguin colonies by separating out the guano in the color images [8,23,24,25]. The eBee UAS followed a pre-programmed three-dimensional flight path guided by a precision GPS sensor, a high-resolution barometer, ground-sensing camera and wind-speed indicators as in Arona et al (2018) [52].
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