Using Temperature Dataloggers to Monitor Bird Nesting Success

Avian reproductive success can be used to assess a range of habitat quality and life history attributes. Monitoring the success of birds’ nests, however, can be a costly and time-consuming endeavor. First, the nests have to be found, and then they have to be visited regularly to identify dates of key events, such as hatching and fledging. Researchers at the University of Vermont have used simple temperature logging sensors to demonstrate that it is possible to reduce the costs of monitoring by up to $12,500 over five years.

Researchers used a device called an iButton, which is a light-weight, self-contained temperature logger the size of a dime. It turns on at specified intervals (every 15 minutes in this study) and records temperature. This data is later retrieved through downloading on site. Depending on the number of loggers purchased, the cost for the hardware and the interface for downloading data was between $2500 and $3400 at the time of this study.

To test these devices, researchers found 161 nests encompassing 16 species along rivers in the Champlain Valley of Vermont, and installed iButtons on 34 of them, with control loggers mounted nearby. iButtons were partially coated in plastic, and a filament was glued to the base. In the field, this filament was threaded through the nest and anchored to surrounding vegetation. Field installation took less than three minutes.

By measuring the difference in temperature between the nest and the ambient environment, researchers could tell when the temperature at the two locations converged. When the nest temperature reaches the ambient environment temperature, this indicates the birds either fledged or were predated. Nests received regular field visits (every 2-3 days) in addition to temperature logging, to compare the precision of field visits with that obtained by loggers.

After a season of monitoring, the researchers found

• Temperature loggers were more precise in capturing date of nest fate than researcher visits
• There was no observable impact on nest success from iButton deployment,
• It’s possible to deploy in a greater range of environmental and nest conditions than previous, studies have attempted,
• On average, field visits to nests could be reduced by 15%, meaning one out of six field technicians could instead spend their time finding more nests.

When budgets are constrained, employing field technicians to monitor nests means forgoing additional nest searching to pay for the time needed to monitor the nests already found. With iButtons, monitoring visits are reduced, freeing up technicians to search for additional nests and deploy more iButtons. The use of this technology could expand the capacity for bird nest monitoring for a range of species in the Champlain Valley and beyond, giving us a richer and more nuanced picture of how nest success relates to key attributes of ecosystem functioning and habitat quality.