Cathemeral Behavior of Piping Plovers (Charadrius melodus) Breeding along Michigan’s Lake Superior Shoreline

Riley Waterman,Jason Garvon

doi:10.3390/birds3010006

Abstract

Shorebirds commonly exhibit cathemeral activity and commonly forage throughout a 24 h period. Conservation of endangered shorebirds should then extend to protection at night, yet little data exists on overall time budgets of such species at night. The Great Lakes population of piping plovers (Charadrius melodus) is the smallest and most endangered, making each breeding pair an essential part of recovery. Intense monitoring of breeding individuals occurs during the daytime, yet we have little understanding of the time budgets of plovers at night. To gain better insight into the cathemeral behavior of plovers we recorded behaviors of 12 plovers from along Michigan’s Lake Superior shoreline during both day and night in 2018 with the use of a night-vision-capable camera, and compared time budgets of plovers between daytime and nighttime. Overall, piping plovers spent more time and a greater proportion of their time foraging at night and more time devoted to being alert during the day. These differences were especially evident during the chick rearing phase. Limited observations suggest that copulatory activity may also be more common at night. Likely, the threat of avian predation on this population drives the increase in nighttime foraging, despite decreased efficiency. Recognizing the importance of decreasing potential for disturbance during the night should be considered in future management strategies regarding the recovery of this endangered species.

Highlights

The breeding population of piping plovers in Michigan’s eastern Upper Peninsula along Lake Superior was once pivotal in recovery when the population was small but has since come to represent a small regional pocket of breeding activity that annually consists of 6–10 breeding pairs [28] and is 190–230 km north of the major breeding population at Sleeping Bear Dunes National Seashore which represented 33 of the total 67 breeding pairs in 2018 [29]
During the 2018 breeding season we examined the cathemeral behavior of piping
During the 2018 breeding season we examined the cathemeral behavior of piping plovers by creating time budgets using seven different behaviors displayed by 12 plovers plovers by creating time budgets using seven different behaviors displayed by 12 plovers observed during both day and night

Summary

Introduction

Cathemerality refers to animal activity throughout both light and dark phases of the 24 h cycle [1,2], and is commonly reported in primates, e.g., [3,4], and other mammals, e.g., [5,6]. It has not been widely used to describe bird behavior, despite numerous studies of both nocturnal and diurnal foraging of bird species, e.g., [7,8,9]. Shorebirds commonly exhibit cathemeral behavior [9,10,11,12], and may use different foraging techniques between daytime and nighttime (i.e., visual or tactile) [10,11,13], or forage in different areas between daytime and night time due to food availability, predation risk, and human activities [11].

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Discussion

Conclusion