Birds

While walking through a forest in spring we often marvel at the vivid greenness, listen to birdsong, and mind our steps in order not to get into a spider’s web. Enjoying the moment, we usually do not think about the complexity of this environment, nor the intertwined relations among all of its elements. However, what slips our attention is not going unrecognized by Maia Persche – a Master’s candidate in the SILVIS lab. In her research, Maia seeks to discern the role of topography in the timing of vegetation growth onset within forest, and to understand how topographic position potentially shapes songbird habitat.

To gain insight into these questions, Maia undertook the challenging tasks of measuring tree phenology, and conducting invertebrate and bird surveys in her study area in the Baraboo Hills of Southern Wisconsin. In order to relate these data to each other, each type of survey was carried out at the same 70 locations during narrow time windows throughout the season. Tree phenology surveys occurred in April and May, and invertebrate and bird surveys were repeated throughout the bird breeding season, or until the end of July. At each location, additional data was collected on temperature, tree species composition, and site characteristics. Over the course of two field seasons, she detected 53 insectivorous bird species, and tracked the seasonal abundance of common invertebrate orders (Lepidoptera, Araneae, Hemiptera, Hymenoptera, Diptera and Coleoptera).

Based on only a portion of measurements collected, Maia has already drawn some interesting preliminary conclusions. Trees leafed out slightly later in stream gorges than in uplands, and although invertebrate biomass was related to tree phenology, it did not appear to follow a predictable yearly pattern. However, sheltered stream gorges supporteded high invertebrate biomass during the mid- and late summer. This could be important for double-brooded bird species that still have active nests in July and can be limited by food availability in some habitats. Overall, stream gorges supported the highest bird species richness, perhaps due to stable food resources or habitat complexity. Also, a strong association has become evident between particular tree species and invertebrate orders, suggesting that tree composition may be more important than topographic context for some folivorous invertebrates.

Under shifting climate conditions in deciduous forests, it is important to identify areas where habitat quality for species is likely to remain high. To assess bird territory quality in different topographic situations, Maia used feather growth bar analysis for a few widely distributed forest species (Wood Thrush, Red-eyed Vireo, and Ovenbird). She captured birds throughout her study area using mist nets, playback calls, and bird models. She then banded the birds, took structural measurements, and pulled one tail feather. Growth bars, or horizontal bands along the feather, correspond to diet richness of the bird while the feather was growing, and will be used to assess social dominance and habitat quality. Although this approach provides a detailed look at habitat quality, it is also the most difficult to carry out in the field.

Maia has collected a large amount of data, and analyzing the relationships among different factors and trophic levels is somewhat daunting, but she approaches it with great enthusiasm. Maia is currently working to determine how bird territory density varies according to topographic context. It is definitively worth staying tuned to see what new results Maia uncovers!

Ph.D. student Kristin Brunk works in the old-growth redwoods of central California to understand the efficacy of current management for Steller’s Jays (Cyanocitta stelleri) and the implications of this management for the federally threatened Marbled Murrelet (Brachyramphus marmoratus). Both are native bird species in the redwoods, but Steller’s Jays are a synanthropic species, meaning they benefit from associating with humans, while Marbled Murrelet populations have severely declined. As populations of Steller’s Jays have increased, they have threatened the viability of Marbled Murrelet populations mainly through nest predation. Nowhere has this threat been more dire than in protected campground areas in remnant patches of old-growth forest. These areas have Steller’s Jay populations that are twice as high as in non-human dominated forests, and these campground areas also represent 60% of all remaining Marbled Murrelet nesting habitat in central California.

Murrelet reproduction is naturally slow, as adults only produce one chick per year, but in central California where Steller’s Jay populations are subsidized by human foods, about 80% of Marbled Murrelet nests fail, due mostly to predation. Reducing corvid predation would help boost murrelet reproduction, which is believed to offer the highest probability of Marbled Murrelet population recovery in central California. In 2013, in an attempt to combat corvid predation, California State Parks implemented multiple non-lethal strategies to manage Steller’s Jays. These included improving trash management, deploying noxious murrelet mimic eggs to create taste aversion to murrelet eggs in corvids, and the “Crumb Clean” campaign, an effort to educate campers about the harm of feeding corvids and eliminate corvid access to camper food. The crumb clean campaign requires campers to properly store or dispose of all foodstuffs in their camp. Through the elimination of this food source in the campgrounds, the hope is that jay populations will decrease, allowing more murrelet nests to succeed. Brunk’s research focuses on comparing jay density, home range size, body condition, and diet between pre- and post-management jay populations to determine if these management strategies have been successful.

Brunk focuses her work within the campgrounds of Big Basin Redwoods State Park by capturing Steller’s Jays in mist nets. Once she has captured a jay, Brunk takes a tail feather sample to determine the bird’s body condition and a flight feather sample to determine what the bird has been eating. Body condition is determined by measuring feather growth bars, and Brunk deciphers how much human food the jays eat by performing stable isotope analyses on flight feather samples. Each jay is also banded with a unique color combination, so individuals can be identified without re-capturing them, and males are fitted with a backpack-mounted radio-transmitter. By tracking birds with radio-transmitters, Brunk is able to understand how jay home range sizes have changed since management started. Despite a perpetual battle of wits with the extremely intelligent Steller’s Jays, Brunk has successfully banded about 85% of the jays in her study area.

In addition to her research, Brunk is also incredibly active in education and outreach throughout her study area. She gives talks at Big Basin Campfire Programs to educate the public about Marbled Murrelets and Steller’s Jays. Brunk conducts banding demonstrations so campers can see exactly how she captures the jays, and they can often participate in the release of banded jays. And as she walks through the campgrounds tracking birds with radio-transmitters, she frequently answers campers’ questions about the giant metal antenna she is carrying. Brunk works hard to foster good relationships with the other users of her study area and is passionate about sharing her work to promote better public understanding of management initiatives such as the crumb clean campaign.

Brunk plans to complete one more field season in 2019, but her research is far from over. Brunk is also working to evaluate a Habitat Conservation Plan (HCP) and its effectiveness at conserving Marbled Murrelet habitat on private land. Habitat Conservation Plans are a commonly used management strategy, with over 1000 HCPs currently active, but the efficacy of these plans has not been well-tested. Brunk hopes to determine if HCPs are an effective management technique, using the Marbled Murrelet as a case study. Overall, Brunk’s research aims to understand the effectiveness of management strategies and conservation of federally threatened species. Ultimately, what she discovers will be used directly in adaptive management strategies that will be paramount in preventing the extinction of the Marbled Murrelet. Along the way, Brunk hopes to uncover strategies and techniques that will apply to the conservation of other species in the future.