An Interview with Dr. Rosalind Renfrew

Roz Renfrew holding a Bobolink You have been studying Bobolinks for some time now. What sparked your interest in Bobolinks in the first place?

Bobolinks may be charismatic, with their bubbly song and striking colors, but what really drew my attention was their incredible migration, and the fact that we knew next to nothing about their life on the other side of it. 

The results of the 2nd New York Breeding Bird Atlas were published recently and documented a modest 8% decrease in blocks with nesting Bobolinks compared with the previous survey in 1980-85. What can you tell us about Bobolink population trends in Vermont and across the country? Are Bobolinks a Species of Special Concern in Vermont?


 
Yes. In Vermont the distribution of Bobolinks has not changed appreciably in the last 25 years, but where they do occur, abundance has been declining. They occupied 6 percent fewer blocks in the second Vermont Breeding Bird Atlas compared to the first Atlas. What is of more concern, however, is that the Breeding Bird Survey shows an annual decline of 2.9% for Vermont from 1982 to 2007. Vermont is part of a larger-scale trend: Bobolink populations have been decreasing by 1.8% per year range-wide since 1970, and declines have been most severe during the last 10 years. Canada has lost 88% of its Bobolink population since 1970. Because declines have continued unabated during the last 10 years and threats to populations persist, Canada added the species to its Threatened list in 2010.

Bobolinks, of course, are champion migrators. You have obtained some fascinating results concerning Bobolink migration using geolocator technology. What did you discover? What surprised you most about Bobolink migration?

Geolocators represent an innovative new technology for analyzing bird migration patterns. Small light-sensitive chips attached to captured birds record and store data based on the time of sunrise and sunset that can be evaluated with software when the birds are recaptured. The data we obtained from only three Bobolinks (2 from VT, 1 from NH) shed dramatic new light into the location and timing of migration stopovers, routes, and wintering grounds. Two birds that were breeding 7 km apart in the Champlain Valley did not winter together, nor did they share the same migration route. Each of the three birds had 2-4 stopovers per migration, and some fall stopovers lasted for weeks. The Bahamas are a short but potentially important stopover during spring migration, and Colombia and Venezuela appear to be important stopovers in the spring and fall, respectively. Although Bobolinks do move around to some extent during winter, they do remain in the same general area for 2.5-3.5 months. All three birds left their wintering areas during the first week of April to migrate north (it was previously thought that they departed in early March). These are just some of the highlights.

The biggest surprise was a transoceanic flight by one bird of 1900 km (1100 mi) within 24 hours - which means the bird flew an average of 50 mph for 24 hours. I checked and rechecked my data, and consulted with the developers of the geolocator software, and it is a certainty that the bird made this trek as part of its migration north. Undoubtedly, it had the help of a tailwind, and the weather data from the area on that day support this assumption. Even so, I never thought this species to be capable of migration speeds similar to those of shorebirds.

My colleagues and I hope to retrieve more geolocators this year that will provide insights about the migration patterns, timing, and wintering areas of populations across the breeding range.

A few years ago you discovered a huge, previously unknown flock of Bobolinks feasting in the rice fields of Bolivia and speculated that there might be more. What is the significance of this finding? Are there more mega-flocks of Bobolinks in South America yet to be discovered?

This was the first time that such enormous flocks were documented, although it was nothing new to the local farmers. After this discovery, biologists in Argentina searched in rice fields and also found large Bobolink flocks. All observations on the wintering grounds, however, collectively account for less than 5% of the entire Bobolink population; there are clearly other areas supporting wintering Bobolinks that have not been discovered. I suspect that Bobolinks also overwinter in the wetlands of the Pantanal (southern Brazil), but this area has so far only been described as a migratory stopover.

It’s hard to believe that Bobolinks are regarded as pests in South and Central America, whereas they are revered in the United States and Canada as an iconic summer bird. You have surveyed farmer’s attitudes toward Bobolinks in the southern hemisphere. What did you find? What can be done to change these attitudes?

First and foremost, it is critical to recognize that there is actually little difference in attitudes between farmers in North and South America- just different pests. A rice producer in Bolivia is no different from a sunflower producer in the U.S. struggling to keep Red-winged Blackbirds at bay. Although birdwatchers may enjoy the Bobolink, scathing remarks about the species appeared in farmers’ journals in Canada once the species was declared Threatened and had the potential to disrupt haying operations (farmers now have a 3-year exemption while a plan is developed). If you’re watching a species disrupt your operations, or literally eat into your income, probably nobody is going to change your attitude.

Attitudes in Bolivia varied depending on the farmer’s experience with the Bobolink. Newer rice farmers weren’t bothered by the birds, while those who had been fending off the species for decades tended to have zero tolerance. My sense was that estimates of the damage caused by Bobolinks were often exaggerated by the latter group, and this has been seen with other species in other countries. But the threat to farmers is very real and needs to be addressed. Determining just how much (or how little) the birds are eating may help change perceptions, and may help farmers populate a cost-benefit analysis with some real numbers.

The approach to take is not to talk farmers out of their perceptions, but rather to offer information and most importantly, attempt to develop solutions. While Canada works hard to bring back its population of Bobolinks, we need to be thinking about how to avoid exacerbating the problems for rice growers far south of us, whose control efforts may only make recovery here more difficult and expensive. The north hand needs to know what the south hand is doing, and vice versa; a holistic approach is needed.

There are threats to Bobolinks in the northern hemisphere, too, especially the timing of hay cutting that coincides with Bobolink nesting and breeding. When you look at threats to Bobolinks across the board, which ones are most important to focus on from your perspective?

Threats have so far been addressed only on the breeding grounds, and it is critical to continue to promote management practices that maximize nest productivity. Research from the Champlain Valley (carried out by Noah Perlut and Allan Strong at UVM), however, shows that even the best case scenario on hayed lands will slow but not halt declines. A study in Iowa on non-hayed lands found that to obtain self-sustaining populations of Bobolinks, increasing survival during the non-breeding season was essential. In both cases, survival is an important part of addressing population declines. We need to learn whether, how, and where we can take conservation measures to increase survival during migration and winter, while continuing to maintain and even create quality nesting habitat. In essence, a holistic approach that addresses threats throughout the Bobolinks annual cycle will be needed to get (and keep) Bobolinks back on track.