AOS is proud to recognize the students and postdoctoral researchers who are receiving research funding through our 2019 Student and Postdoctoral Research Awards! These annual awards, each up to $2500, honor early-career ornithologists doing research that advances our understanding of birds and their conservation. The research awards committee puts a great deal of time and thought into evaluating applications each year, and we appreciate their efforts!Continue reading “Congratulations to the 2019 Student & Postdoc Research Award Winners”
Linked paper: Urban background noise affects breeding song frequency and syllable-type composition in the Northern Mockingbird by M.J. Walters, R.P. Guralnick, N.J. Kleist, and S.K. Robinson, The Condor: Ornithological Applications.
Imagine having a conversation with someone next to a very busy intersection at rush hour. You can’t hear one another at a normal volume, so what do you do? You could talk louder, maybe wait for the noise to die down, or simply pick up your belongings and move to a quieter setting to converse.
Our research shows that if you’re a Northern Mockingbird, one of North America’s most famous avian songsters and the state bird of five U.S. states, you adjust to noisy settings by conversing at a higher pitch. Northern Mockingbirds’ songs are incredibly complex, made up of hundreds of different elements, and we also found that urban mockingbird songs include more high-pitched elements.
So why raise your pitch? Noise in urban environments overlaps most strongly with lower-frequency bird vocalizations, so mockingbirds may be increasing the pitch of their songs to avoid being drowned out by urban background noise. However, mockingbirds also love to mock things, so it’s possible that individuals mimic higher-pitched sounds more often in urban environments. In any case, the Northern Mockingbird is a great example of a bird adapting to urban habitat. Previous research in our lab has shown that not only is this species more abundant in urban areas, it also adjusts its nesting, foraging, and anti-predator behavior in these settings. The acoustic flexibility we found in our study may add to their ability to coexist with urbanization and people.
Because mockingbirds love to mock other bird species in their environment, it also makes sense to ask how much of a role surrounding bird communities play in the characteristics of their songs. This is important, because a male who’s a prolific impressionist may be very attractive to female mockingbirds. Future research aims to look at whether urbanization affects the quality of mockingbird songs via changes in bird diversity. If this is true, then human disturbance could be indirectly impacting the evolutionary trajectory not only of Northern Mockingbirds, but of other mimicking species as well.
When I started my master’s degree at the University of Florida, I actually had no intention of working with mockingbirds. I originally planned to do a project overseas, but my advisor and I quickly realized that was unrealistic. After a few mild panic attacks and brainstorming sessions I turned to urban ecology, a topic I had recently developed an interest in. Our lab had done long-term studies on urban mockingbirds, but no one had looked at what was, in my opinion, the most fascinating part of mockingbird life history — their songs. So the stage was set, the field gadgets were bought, and the grant proposals were accepted, sort of. After two years of blistering Florida summer heat and several strange encounters with locals asking what the heck I was doing with recording equipment, the project was complete and the results are now in! I just want to thank AOS for publishing my first first-author manuscript; it’s been an absolute pleasure working with this amazing journal.
In the lead-up to our annual meeting in Anchorage, we’ll be highlighting the winners of this year’s AOS awards on the blog. This week, the 2019 Painton Award.
Every two years, the American Ornithological Society bestows the Harry R. Painton Award for a paper published during the preceding two years in The Condor: Ornithological Applications that has made an exceptional contribution to ornithology. The Harry R. Painton Award for 2019 is presented to Jason D. Carlisle (University of Wyoming and Western EcoSystems Technology, Inc.), Anna D. Chalfoun (US Geological Survey and University of Wyoming), Kurt T. Smith (University of Wyoming), and Jeffrey L. Beck (University of Wyoming) for their paper “Nontarget effects on songbirds from habitat manipulation for Greater Sage-Grouse: Implications for the umbrella species concept,” published in 2018.
The authors addressed what is likely to become an increasingly important issue in avian conservation: do efforts to mitigate and improve conditions for an “umbrella” species actually benefit other “background” species that share their habitat? The authors used a rigorous before-after control-impact design over a three-year period to determine whether management of habitat for the habitat specialist Greater Sage-Grouse (Centrocercus urophasianus) would benefit a trio of songbird species that co-occur with sage-grouse by comparing songbird abundance, nest density, and nest success before and after mowing of sagebrush intended to improve brood-rearing habitat for sage-grouse. The authors showed that mowing benefitted the non-sagebrush specialist Vesper Sparrow (Pooecetes gramineus), but that the sagebrush-steppe dependent Brewer’s Sparrow (Spizella breweri) and Sage Thrasher (Oreoscoptes montanus) experienced a different fate. Sage Thrasher abundance declined after habitat modification for sage-grouse, while nest abundance dropped to zero for both Brewer’s Sparrow and Sage Thrasher in managed (mowed) habitat. Ultimately, the authors caution that a more “nuanced” view is needed that considers the varied responses of species syntopic with so-called umbrella species and that long time scales are likely needed to evaluate fully the utility of the umbrella species concept.
This year, the AOS Publications Awards Committee felt that two additional papers deserved recognition as runners-up for the Painton Award: “Migratory connectivity of Semipalmated Sandpipers and implications for conservation” by S. Brown, C. Gratto-Trevor, R. Porter, E. L. Weiser, and 19 others, and “Island life and isolation: The population genetics of Pacific Wrens on the North Pacific Rim” by C.L. Pruett, A. Ricono, C. Spern, and K. Winker, both published in The Condor in 2017. The Harry R. Painton Award is given in odd-numbered years and consists of a cash prize of $1,000; funds for the award come from a bequest from Mr. Painton. A list of previous Painton Awardees can be found at americanornithology.org/content/aos-painton-award.
Linked paper: Liberalized harvest regulations have not affected overabundant Snow Geese in Northern Manitoba by D.N. Koons, L.M. Aubry, and R.F. Rockwell, The Condor: Ornithological Applications.
As many marshes along the Gulf Coast were drained in the late 1970s, Snow Geese that had used them as wintering areas began shifting to agricultural land instead. Leftover crops in farm fields provided them with a generous new winter and spring diet, and the population began growing at an unprecedented rate. While they have ample habitat in the south, the growing number of geese, coupled with their destructive foraging behaviors, has led to increasing and widespread habitat destruction in the Arctic coastal habitats where they breed.
In response to this habitat degradation and the resulting negative impacts on other species, the U.S. and Canada attempted to reduce the size of the population by liberalizing the regulations on Snow Goose hunting beginning in 1997. This included increasing bag and possession limits, expanding the hours during which hunting is permitted, allowing the use of unplugged shotguns and electronic callers, and instituting a spring conservation harvest. Adult mortality has a greater relative impact on the growth rate of this species than any other demographic variable, so wildlife managers hoped that removing more adults from the population through hunting would help bring it under control.
Adaptive Harvest Management is an approach used in North America that examines the impacts of management decisions and readjusts those decisions as necessary to meet management goals. We used our 50-year database on more than 100,000 Snow Geese banded on Canada’s Cape Churchill Peninsula to assess whether the new regulations were having the desired effect of increasing adult mortality. Using new analytical techniques, we could estimate the rates of both hunter and non-hunter deaths of adult geese and see whether those rates changed when the new hunting regulations were implemented.
Adult harvest mortality has stabilized at a low level, with only around 3% of adult geese being killed by hunters in a given year, probably because the sheer abundance of Snow Geese in this population has overwhelmed the number of hunters. The number of North American hunters has not increased in recent years, and most hunters are only willing to harvest enough geese to meet their family’s needs. Adult non-harvest mortality declined through the 1970s and 1980s to trivial levels (around 1% per year), but has increased recently and now fluctuates between 10% and 19% per year. Unfortunately, the combined mortality isn’t enough to limit the species’ growth, and the population continues to increase in size.
In light of our results, the next cycle of Adaptive Harvest Management needs to consider the potential causes of the increase in non-hunting mortality and its year to year variability, especially since such variation actually reduces overall population growth rate. We also suggest that management agencies further refine hunting regulations to increase the harvest per hunter and make efforts to increase public participation in hunting, perhaps through outreach to currently underrepresented groups.
The authors are all associated with the Hudson Bay Project. More about our work can be found at http://research.amnh.org/users/rfr/hbp.
Linked paper: Speciation despite gene flow in two owls (Aegolius ssp.): Evidence from 2,517 ultraconserved element loci by K. Winker, T.C. Glenn, J. Withrow, S.G. Sealy, and B.C. Faircloth, The Auk: Ornithological Advances.
Scientists have long thought that for two related populations of birds to evolve into separate species, they needed to be completely separated. This usually means the kind of total separation produced by isolation on islands or by features such ice sheets, mountain ranges, or rivers. However, the complex distributions and migratory nature of many birds mean that long-term total separation of bird populations, long the assumption in speciation research, is actually not necessary for speciation to occur. As we’ve tried to better understand how bird populations diverge, other ways of explaining speciation have begun to receive more attention, and it’s becoming increasingly clear that speciation can happen even with low levels of gene flow. Learning how this can happen in migratory taxa has become an important focus in ornithology.
Northern Saw-whet Owls (Aegolius acadicus) occur across much of North America. A small, non-migratory population is isolated on the islands of Haida Gwaii in British Columbia (A. a. brooksi), and the nominate mainland form (A. a. acadicus) passes through these islands during migration but does not stop to breed. So, these two populations overlap during some parts of their annual cycle but not during others. Presently considered a subspecies, brooksi feeds heavily on intertidal invertebrates in winter and has strikingly dark plumage compared to the migratory form, acadicus. Although their geographic context suggests the potential for gene flow, no one has ever found any intergrades between the two populations, suggesting that ecological factors are playing a role in maintaining their separation. Reconstructing how these owls diverged is difficult, because we can’t know the exact history of the distributions and ecological contexts that preceded what we observe today in this glaciated region. However, genomic data can be used to test hypotheses about their divergence and tell us what the long-term demographic history has been.
Recent technological advances have vastly increased the amount of genetic data that can be generated to look at divergence in populations. However, it’s important to examine the same parts of a genome so that you are making apples-to-apples comparisons. Ultraconserved elements (UCEs) are sections of the geneome that are relatively easy to find and can be used to assess divergence at population to family and order levels. They provide a similar set of core sequences that increase in variability the further from the UCE you go, allowing the assessment of both deep and shallow divergences at the same place in the genome. We examined over 2,500 separate UCEs to infer the processes under which these data were most likely to have evolved, including population sizes, levels of gene flow, and time of divergence. We found that the model that best fit the data included an initial split between the two populations with a low level of ongoing but skewed gene flow: an average of about 0.7 individuals per generation coming from acadicus into brooksi, and about 4.4 individuals per generation going the opposite direction.
These results support our hypothesis that the divergence between these two forms included low levels of gene flow rather than complete isolation. The low levels of gene flow from nominate acadicus into brooksi, coupled with strong evidence of ecological selection, suggests that the Haida Gwaii owls are on an independent evolutionary trajectory. Nominate acadicus are not staying on Haida Gwaii and breeding with the islands’ owls with the frequency we might expect, and we believe that selection is operating differently on the two populations due to the fact that they focus on resources that are distributed differently in time and space. Despite the history of gene flow between the two populations, brooksi appear to be a young biological species.