Red-Shouldered Hawk Study
in Southern Ohio

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Videos of Nesting Red-shouldered Hawks

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Cincinnati Red-shouldered Hawks


 
Video Monitoring Project - Sara Johnson Miller

In 2011 and 2012, Sara Johnson Miller, then a graduate student at Arkansas State University, joined the research team and used video time-lapse cameras to study nesting behavior in Cincinnati.

The team visited previously-known territories and determined whether they were occupied (e.g., hawk present, nests with fresh sticks or green vegetation lining) – over 250 territories were visited. Nests were monitored from February - June (pre-laying until fledging). At selected nests, 24 h/day digital infra-red video cameras were installed. Cheryl & Jeff did the climbing, while Sara and Melinda provided ground support & processed chicks. Video was recorded with micro-DVRs and the system was powered by a deep-cycle marine battery, and Sara replaced memory cards and batteries on a 3-day cycle.
      

At 15 nests, cameras were installed at occupied nests prior to egg-laying. At 10 nests, cameras went up after eggs hatched, when the nestlings were estimated to be 3-12 days old. The cameras remained in place until the nest failed or fledged young. Within the first week of hatching, nestlings were marked on their heads and backs with Sprayolo non-toxic liquid livestock dye to facilitate differentiation of nestlings in the video. Researchers also climbed again to band (USGS & colored number-letter bands) the nestlings and to re-paint their heads after initial paint began to fade.

Sara extracted data from the 14,800+ hours of video that were recorded. Data extracted during video review included adult behavior during clutch initiation, causes of nest failure, nestling behavior and aggression rates, prey delivery rates and prey types. In addition to the 25 camera nests, the team also monitored the territories that became occupied until nests failed or
 fledged young.
Of the 15 nests that received a camera prior to egg-laying, all pairs laid eggs, and most of these pairs fledged young, while the remaining  nests failed due to predation or nest disturbance. These results show that mounting the cameras during the courtship phase, after the adults occupied the nest, did not seem to disturb the birds. This method also provided more accurate and complete data for an entire nesting period than mounting cameras post-hatching.
 
Of the 10 nests that received and retained a camera post-hatch, mostl fledged young. However, after installing one camera post-hatch, Jeff discovered that the female parent was avoiding the nest, although the male had no qualms about delivering abundant prey. Fortunately, this unusual case was caught within 24-hours of camera installation, and allowed the team to act quickly to remove the disturbing camera and allow behaviors to return to normal. The team is happy to report that this nest successfully fledged all three of its nestlings. This incident illustrated individual birds’ different tolerance levels for nest disturbance. It also furthers the argument for installing cameras prior to egg-laying, because it minimizes consequences of disturbing the breeding pair.


There is good evidence to support the idea that RSHAs have partial incubation, and Sara found start of incubation varied among individuals but many birds began full incubation with the laying of the penultimate egg. The video data showed that more sibling aggression occurred during week 2 than during week 3. These data suggest that the dominance hierarchy is established early and may influence the probability of success of each nestling through the remainder of the nestling period, and perhaps even after fledging.
 
Prey types delivered to nests was similar to that described previously by the team (from conducting direct observation of nests) and included small mammals, frogs and other amphibians, snakes, and invertebrates. This indicates that this population of suburban RSHAs are indeed generalist predators, similar to populations nesting in more typical, remote forested habitats.

Causes of nest failure or chick mortality were depredation by Great-horned Owls and a raccoon, and a three-week battle between a pair of nesting RSHAs and an Eastern gray squirrel, which the squirrel ultimately won. The team is happy to report that the pair re-nested in a new location and successfully fledged two chicks, albeit also in the company of several squirrels!

Our video monitoring of nests provided new insights into incubation behavior and sibling relationships and yielded valuable information on predation and other causes of nest failure.
Sara has finished her Master's thesis and it is available from Arkansas State University.

The video monitoring project would not be possible without the support of the RSHA Team, RAPTOR Inc., Hawk Mountain Sanctuary, The Audubon Society of Ohio, Arkansas Audubon Society Trust, Arkansas State University, and all of the, cooperative landowners in Cincinnati.  

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