As part of my research into how people decide on the biologging technology for their projects, I interviewed Yvan Satgé from the Clemson University about how he has chosen biologgers for studying the black-capped petrel.
The Project Goals
To give some background on the species; the black-capped petrel is a species of seabird native to Haiti and Dominican Republic. In 2004 it was thought that there were less than 5,000 individuals left. As the species winters in the southern United States, it is being considered for a place on the Endangered Species list, with money allocated towards its conservation.
Black-capped petrels nest in montane forests where they burrow under decaying vegetation or loose rocks and soil. Yvan told me about three studies he had taken part in that used GPS data, in 2015, 2019, and 2023. The goal of all three studies was to study petrel behaviour to lead to more effective conservation. They are threatened by multiple different factors both while nesting and at sea.
Choosing the tags
When it came to choosing tags, having worked on multiple prior avian biologging studies, Yvan was able to come up with a “wish list” of tag requirements. Namely, needing a device that was able to record fine scale data to understand the foraging ecology and spatial segregation of individuals and lightweight enough to fit on small birds. This in combination with the limitations of the budget, the environment and the researchers capacity, gave him an idea of what to look for in a tag.
As many seabirds return to the same nest side year after year, it is easiest to go for archival data retrieval or radio download as the birds can be easily located and either have their tags manually removed or placed within range of a base station. As these are both the cheaper options for tags and they were working within a limited budget, both were considered.
However, as black-capped petrels nest in burrows, a base station would get limited signal and they did not have the means to have people regularly hiking up the mountains to the nest sites to manually collect data. Archival data was not considered as this tells you very little about the survivorship of the birds which was a key concern of the study of an endangered species.
Yvan and his team also knew that they would need solar powered biologgers, as they were also looking to get long term data and having a standard battery that lasted that long would have increased the weight past the limit for the birds.
They decided on using sutures to attach the tag to the bird as using a backpack or harness on the black-capped petrel could have been caught in roots or twigs entering or exiting its burrow. Any tag would have to come with casing to attach the casings to.
“It's always a balancing act between what you want, what you really need and what you can get. And for smaller species, I mean the black-capped petrel actually is not super small, the size of a pigeon, but you're still limited on what kind of data you can get.”
Photo credit: R. Ronconi (2014)
Consequently, they decided to use solar powered satellite Argos PTTs. This would allow reliable data collection for the length of the study. Once they had decided on the type of tag they needed to decide where they would get the tags. The biggest limiting factor was the weight with few manufacturers making tags that small.
While working on a pelican biologging project, Yvan had used tags from Geotrak, Inc and found them very reliable with good data collection and a company that was quick to respond to queries. They decided to use Geotrak’s 5g PTT for the project. As satellite tags are more expensive they were only able to put trackers on a few birds.
How did it go?
The deployment of the tags was largely successful with the tags working well for that first study. So in 2019 they again turned to Geotrak for tags. This time they were also able to use two PTTs from Microwave Telemetry. They were donated by colleagues from a similar project in another institution thus were available for Yvan to use on the black-capped petrel. This time, they were able to deploy ten tags in total, two from Microwave telemetry and eight from Geotrak.
It is worth mentioning that another option in 2018 were Mataki tags, which were more similar to DIY biologgers where you bought the tag and then could adjust it to fit the study species. They had been successfully used to track shearwaters in Australia. Yvan saw that they had been used and began to research if they could be applied to his project. What made him decide to try them was seeing that someone within his network had used them and therefore was available to answer questions about putting them together. As they were very cheap he tried them but ultimately was not able to make them work for the project and thus went with the other tags. Yvan started two discussion threads on WILDLABS to share tips about using Mataki tags: using the tags, and using the base-stations.
When speaking of the decision making process, Yvan highlighted that it is most common to use tags that you have experience with or people within your network have experience with. This is because the reliability of the tag is so important. When speaking about another project he advised the tag process on, the tags that project worked with malfunctioned and needed to be replaced by the manufacturer.
“But it's not just the money that the manufacturer is wasting, it's also all the money that is wasted in gathering the people to capture the birds, all the logistics, the permitting, all the other parts that you need to do that you’re wasting, basically with a tag that doesn't work. And so that's why we wanted to choose one manufacturer, even if it's not the best one, but one where we know it works. We're gonna keep going with that one because we don't want to take the chance of wasting all that field work”
This is why some level of experience with the tags is so important. While the tags from Geotrak and Microwave Telemetry were good for the project in general the low budget of the project meant that only a few tags could be purchased so Yvan thought it is too low a sample size to comment on the usability of the tags as a whole.
This case study helps illustrate the need for reliable tags in many projects where they are working within small budgets and tagging few individuals. And how the process for finding tags will have to prioritise this by ensuring that the tags chosen have already been tested on similar projects.
With thanks to Yvan Satgé for speaking to me about his experience and providing the photo of the tagged black-capped petrel. Look out for the next article in my series looking at tags for marine environments and how those are used on bluefin tuna, tiger sharks, basking sharks and great white sharks!
Banner photo credit: cotinis