Climatic extremes influence spring tree phenology and migratory songbird foraging behavior

In the Upper Midwest of the United States,
fire suppression has resulted in succession of
savanna and forests that differ in both plant community composition and vegetation structure from
their condition prior to Euro-American settlement. Furthermore, variations in weather affect
spring phenological events and potentially alter
synchronous relationships of migratory songbirds
with their seasonal resources. Our goal here was
to understand how annual variation in phenology of four tree species—northern red oak (Quercus
rubra), eastern white oak (Q. alba), sugar maple
(Acer saccharum), and red maple (A. rubrum)—affect
foraging behavior of migratory songbirds during
spring migration. Oaks currently have poor regeneration, whereas maples have good regeneration
in forests in the Upper Midwest. A typical temperature regime in 2009 coupled with a record
warm winter and early spring in 2010 provided a
natural experiment for addressing our goal. In the
spring and early summer of 2009 and 2010, we
monitored migratory songbird foraging behavior
and collected data on tree flowering and leaf-out
phenology for 160 replicate trees of the four study
species at the Kickapoo Valley Reserve in southwest Wisconsin. In 2009, 15 species of migratory wood-warbler (F. Parulidae) arrived at the
stopover study area in late April and were present
until late May. Birds foraged heavily on flowering
northern red oak and, to a lesser extent, on flowering eastern white oak and sugar maple. Red maple
was not preferred by wood-warblers. In 2010, the
arrival date and duration of stay among the 15 species of wood-warblers was similar to 2009, yet
the frequency of use of the four tree species was
reduced by 60%. Northern red oak, sugar maple,
and red maple achieved summer condition 2 to
3 weeks earlier in 2010 than 2009, but these tree
species were not preferred by the wood-warblers.
Instead, eastern white oak, which flowered from
early to late May, was the preferred foraging substrate in 2010. Our findings suggest that the flowering and early leaf-out phase of trees provides
important resources to migrant wood-warblers
that are apparently absent from trees that are more
phenologically advanced. Our results also suggest
that managing for heterogeneity in tree species,
including early and late flowering species, as well
as maintaining early successional tree species in
the landscape, may be an important consideration
in maintaining wood-warbler population levels
under a variety of climate conditions.

File: Wood__Pidgeon_2015_Studies_in_Avian_Biology_Phenology.pdf

In the Upper Midwest of the United States,
fire suppression has resulted in succession of
savanna and forests that differ in both plant community composition and vegetation structure from
their condition prior to Euro-American settlement. Furthermore, variations in weather affect
spring phenological events and potentially alter
synchronous relationships of migratory songbirds
with their seasonal resources. Our goal here was
to understand how annual variation in phenology of four tree species—northern red oak (Quercus
rubra), eastern white oak (Q. alba), sugar maple
(Acer saccharum), and red maple (A. rubrum)—affect
foraging behavior of migratory songbirds during
spring migration. Oaks currently have poor regeneration, whereas maples have good regeneration
in forests in the Upper Midwest. A typical temperature regime in 2009 coupled with a record
warm winter and early spring in 2010 provided a
natural experiment for addressing our goal. In the
spring and early summer of 2009 and 2010, we
monitored migratory songbird foraging behavior
and collected data on tree flowering and leaf-out
phenology for 160 replicate trees of the four study
species at the Kickapoo Valley Reserve in southwest Wisconsin. In 2009, 15 species of migratory wood-warbler (F. Parulidae) arrived at the
stopover study area in late April and were present
until late May. Birds foraged heavily on flowering
northern red oak and, to a lesser extent, on flowering eastern white oak and sugar maple. Red maple
was not preferred by wood-warblers. In 2010, the
arrival date and duration of stay among the 15 species of wood-warblers was similar to 2009, yet
the frequency of use of the four tree species was
reduced by 60%. Northern red oak, sugar maple,
and red maple achieved summer condition 2 to
3 weeks earlier in 2010 than 2009, but these tree
species were not preferred by the wood-warblers.
Instead, eastern white oak, which flowered from
early to late May, was the preferred foraging substrate in 2010. Our findings suggest that the flowering and early leaf-out phase of trees provides
important resources to migrant wood-warblers
that are apparently absent from trees that are more
phenologically advanced. Our results also suggest
that managing for heterogeneity in tree species,
including early and late flowering species, as well
as maintaining early successional tree species in
the landscape, may be an important consideration
in maintaining wood-warbler population levels
under a variety of climate conditions.

Sacred Forests in northwest Yunnan, China – a conservation priority?

Hillside of village sacred forest with view of valley below

In northwestern Yunnan, China, certain patches of forests are considered sacred. What does that mean? It means that people go into the forest to pray or to offer gifts to their same gods because they believe their lives will be blessed and successful if they do so. Jodi was interested in the biodiversity of sacred forests and inventoried which bird species occur there. Jodi end up publishing a bird field guide both in English and in Mandarin as a result of her work (http://silvis.forest.wisc.edu/pubs/birds-shangrila).  Later on, Teri conducted interviews with locals because she was interested in understanding how local people see sacred forests, but also to understand if an extra conservation status was necessary in order to preserve these little patches.

Conducting survey about sacred village forests

As a result of the interviews, Teri came to the conclusion that people do not see the forest as a wildlife habitat or as an area that provides other ecosystem service such as clean water or soil protection. Instead, the sacred forests serve the single purpose of pleasing the gods and thereby ensure that people’s lives go on smoothly. This perception of the forest is the same across genders and age groups, which indicates that unless there is a major shift in the local belief system, there is no immediate danger of losing village sacred forest areas.”

Measuring trail use with remote detectors

Max made a technological contribution to both the fields of wildlife ecology, and parks & recreation by developing a device to measure how heavily trails are used. His goal was to quantify both group size and frequency of groups (groups/hour) along a given trail, but the available solutions were more than his research budget could manage. Having someone count hikers all day along several trails required more personnel than was practical. Meanwhile, he worried that sampling use in small time periods would provide representative data, because trail use varies throughout the day. The idea to use an automatic sensor was desirable, but the options on the market were too expensive. So he collaborated with someone with technical expertise to invent a tool that met his needs.

Components of the Trail Monitor inside a protective weather-proof box

The solution was found in open source software and DIY hardware. First, he acquired a passive infrared (PIR) sensor that can detect warm-bodied objects that passed by (these are the same types of sensors that control automatic light switches by detecting when someone walks into a room). Then, he connected this sensor to an Arduino Uno board (http://www.arduino.cc/) that supports open source software. The board receives input from the sensor, and can be controlled by a user-written script. This is connected to a data logging shield (http://www.adafruit.com/product/1141) which contains a clock and an SD card to store data. Then, the data can be imported Excel sheet. Max used pivot tables to translate the sensor’s detections into his variables of interest. For example, the duration of time the sensor is activated can be used as an index of  the number of people in a group passing by.

Installing a trail monitor along a trail

Max’s invention is a great alternative to what’s commercially available, in part due to the price point: one of Max’s units costs less than $250, in contrast to commercially available counters that cost about $1000/unit. Also, Max’s device can be left out in the woods for about a week between battery replacement. Its relatively small size means it can be easily hidden, which makes it relatively safe from tampering. Thus, Max continues to produce technology that will likely be used by many researchers in the future! “

The differential importance of aquatic insect productivity on terrestrial, insectivorous bird guilds.

In an unusual twist, Paul Schilke’s interest in terrestrial birds has led him to study aquatic systems. 

Map of study area (Chequamegon-Nicolet National Forest) with study sites and bodies of water.

Many aerial insectivore bird species, such as swallows and flycatchers, have been declining since the 1980s, but researchers aren’t sure why because little is known about how these birds use the resources around them. This guild is defined by its habit of capturing flying insects in midair, as opposed to the gleaner guild that picks insects off of substrates like leaves or twigs. Many of these flying insects begin their lifecycle in aquatic systems, so Paul thought that the differential decline in the aerial feeding guild might lie in the lakes and streams.Using records from 317 locations within the Chequamegon-Nicolet National Forest in Northern Wisconsin, Paul compared presence of the aerial and gleaner insectivore guild members to estimated insect productivity in nearby lakes and streams, controlling for habitat differences (Figure 1). He estimated insect probability using a model from Bartrons et al. (2013), which used an extensive meta-analysis to determine the relationships between aquatic insect productivity and basic properties of lakes and streams such as temperature, surface area, and clarity. As expected given their feeding behavior, gleaners preferred forested habitats while aerial insectivores preferred more open areas. Interestingly, despite both guilds being insectivorous, aerial feeders demonstrated a strong preference for sites with higher insect inputs, while gleaners had no response (Figure 2).

Figure 2. Scatter plot of response of aerial insectivores (left) compared to response of gleaners (right) to estimated emergent aquatic insect inputs.

Paul hopes that a better understanding of the food resources of aerial insectivores can lead to better conservation measures, and hopefully reverse their long term decline. He will continue his work as a PhD student in the SILVIS lab. 

Working with managers – sharing research results, and getting feedback on research on extreme climate events

Climate change, fluctuating extreme weather conditions, and the resulting change in species’ abundance and distribution, are a major concern for managers of protected areas. The uncertainty of which species will disappear from a protected area, and which will arrive leads to difficulties in creating conservation goals at both small and large scales. In addition, what role do these protected areas serve during extreme conditions, such as intense heat waves or severe drought, for the species that remain
remain? Drs Brooke Bateman, Andrew Allstadt, and Anna Pidgeon have been travelling to meet with managers to show results from their work investigating extreme weather events and changing climate on species populations and distributions.  Involving end user and conservation practitioners to provide feedback on their reserach throughout their project is an ideal way to keep their research goals in line with practical on the ground conservation applications and decisions.

Wayne Thogmartin presenting to the group

Dr Bateman and Dr Pidgeon travelled to Chaska, MN to meet with regional United States Fish and Wildlife Service (USFWS) personnel during the early stages of their NASA funded project to identify the climate and extreme weather data needs of regional climate managers. The goal was to highlight how such data products can be used for targeted research of climate effects on wildlife at the refuge level. Their next workshop led Dr Bateman to Ft. Collins, CO where she presented the groups findings at the National Planning Workshop of the USFWS.  Here, the focus was on broad landscape scale planning for the acquisition of refuges with the aim of buffering wildlife species from climate change related pressures. The trio along with other University of Wisconsin Researchers organized a multi-agency and organization meeting in La Crosse, WI which brought personnel such as the USFWS, Landscape Conservation Cooperative units, United States Geological Survey, the Northeast Climate Science Center, Long Point Waterfowl, as well as Wisconsin and Michigan Department of Natural Resources land managers. This two day workshop included presentations on data and research along with world café style brainstorming sessions to elicit suggestions and feedback from the attendees.. “We found that managers were really interested in maps of climate change and extreme weather for their regions, especially if they showed the uncertainty of the predictions,” said Bateman. The group is trying to keep their finger on the pulse of what data managers are looking for. “Refuge managers really wanted to see predictions specific to their refuge, while regional land managers wanted information at the landscape scale.” This highlights the need to provide data at different spatial scales to meet these various needs.

Project Research participants working with managers of protected areas

As part of a future webpage redesign, data from the project will be available for anyone interested. Users will have the ability to select an area of interest and download relevant data. “We want to always include end users in research, and update our results to meet those needs,” said Batemen. As a result of these workshops, she is currently working on a project using the USFWS designated surrogate species in predictions of species distributions under future changes in climate and extreme weather. These surrogate species were selected as a way to represent other groups of species, such as prairie pothole waterfowl, to provide strategic conservation planning and identify sensitivity of these species as proxies given future change in climate. This is just another way the trio is trying to keep up with the data and research desires of land managers.”

Understanding the effect of extreme weather events on grasslands birds in the U.S.

Climate change entails changes in the average and variability of climate conditions. Under future climate change, it is expected that extreme weather events, such as droughts, will become more frequent or more intense, potentially affecting species and biodiversity. Understanding how species respond to extreme weather events is crucial to understand the impact of future environmental change.

Baird’s sparrow

‘Evaluating how species respond to past can help to inform future responses to climate conditions’, says Jessica Gorzo. Jessica is a 3rd-year Ph.D. student at SILVIS. The main goal of Jessica’s research is to model bird population responses to past weather conditions, so to have a tool to predict bird species responses under future climates.Jessica’s study focuses on fourteen grassland birds in Bird Conservation Region (BCR 17). ‘These grasslands are located in a region of high historic climatic variability and with a regular regime of droughts, which makes it an ideal place to understand species responses to extreme weather events,’ Jessica said.

Map of BCR 17

Specifically, Jessica analyzed past population trends derived from the North American Breeding Bird Survey (BBS) between 1980 and 2012 and their relationships with two climate variables, including rainfall variability and temperature variability. Such an analysis requires the use of Bayesian statistics, as a way to best fit hierarchical models incorporating many underlying sources of variation in the data.The findings from this study are quite important. Six of the fourteen bird species showed significant responses to climate variability, particularly to precipitation. ‘Some species increased with increasing precipitation variability, while other decreased’ Jessica said. According to Jessica, the responses she observed are likely to reflect habitat preferences. For example, species that respond positively to precipitation likely need slightly wet conditions, whereas species that respond negatively use drier areas of the grassland.

Landscape of BCR 17

Climate projections suggest that grasslands are expected to see more severe and frequent droughts, and this study provides useful information to gain insights about the future. According to Jessica, species such as Baird’s and grasshopper sparrows, which depend on patches of wet and vigorous vegetation, could see a negative future under climate change, while others may see less competition from the removal of those species. Through this study, Jessica developed key knowledge for understanding species responses to climate conditions. In the near future, and as she advances with her dissertation, these models will serve to inform scientists and managers to prioritize conservation actions and strategies in the face of climate change. “

Forest birds in the sacred forests of Yunnan, China: what do they need for habitat?

In the northern region of Yunnan Province, for generations, Tibetan villagers have set aside patches of forest for spiritual proposes, also known as Tibetan sacred forests. During previous research Jodi and Eric discovered that sacred forests are keystone structures for conservation of forest bird in a landscape dominated by degraded pastureland.

Figure 1. Mrs. Gould’s Sunbird (Aethopyga gouldiae), which are often found using Tibetan sacred forests as breeding habitat. (Photo: Eric Wood)

They found more than 30 bird species heavily using sacred forests rather than pastureland. This result highlighted the importance of these forests for bird conservation. After this first study, the next step was to understand what characteristics of these forests make them so attractive for bird? Eric said: ‘In order to effectively manage and conserve bird species in the sacred forests, we need to understand the foundational habitat requirement of these birds. Once we know this, they we can begin to make recommendations for conservation applications. We now know that sacred forests support many bird species, the question that remain is why?’ For this, Jodi and Eric collected field data on habitat structure and composition and bird richness and abundance to construct bird-habitat relationship occupancy models. Some key structural variables that the pair sampled were cover of leaf litter, herbaceous materials, shrubs and trees. These variables are indicators of what species need for survivorship: nesting sites, food, refugee and protection. Once data was collected, and back in the comfort of Madison, Eric developed models to relate the explanatory variables with occupancy of over 30 bird species. With this model-selection approach, it was possible to select best-supported habitat-characteristics associated with a particular species occupancy.

Figure 2 Relationships of predicted sample -point occupancy for six bird species with three habitat characteristics representing the ground and sub-canopy layer. Bird species codes: BLPH & LAPH = Blood and Lady Amherst’s Pheasant, YBBW = Yellowish-bellied Bush Warbler, GILT = Giant Laughingthrush, ELLT = Elliot’s Laughingthrush, CVNH = Chestnut-vented Nuthatch, YUNH = Yunnan Nuthatch.

In addition to the structural variables indicating diverse forested habitats, they found that high cover of leaf litter and shrubs are associated with occupancy of understory birds. While doing fieldwork, they observe that some understory specialist look for their food in the litter, where they can find insects underneath the leaves.

Figure 3. Gray-backed Shrike (Lanius tephronotus), which are often found using degraded habitat adjacent to Tibetan sacred forests. (Photo: Eric Wood)

These result highlighted the importance of field observation. In cases where so little life history information is available, field work become a crucial experience to understand what the models are saying to us afterwards. While China continues to grow in population, there is an increase pressure in resources (e.g., wood, water, and land) in less populated regions, as is the case of Yunnan. In addition to learning more about birds that use Tibetan sacred forests as breeding habitat, the result of this research helps inform future forest management in a regional context.”

Change in alpine wetlands of Southwest China and its implications for wintering Black-necked Cranes

Napahai, a high mountain valley wetland in southwest Yunnan Province, is one of three major wintering areas for the Black-necked Crane. With peak counts of the birds at Napahai totaling almost 1,000 birds in the 1960s, the population declined to less than 100 cranes in the 1980s.

Map of China showing the location of Yunnan province, the provincial capital of Kunming and Xiangalila, the Chinese spelling for Shangri-La.

Then, in the early 1980s the creation of water impoundments increased the available habitat for the crane, and the population increased to between 300-500 birds. However, since the mid-1990s, there has been an increase in infrastructure development and agriculture in the valley. While the global population of black-necked cranes has been on the rise over the last 10 years, now estimated at approximately 10,000, the number wintering at Napahai has been steadily declining. Why such a drop in the wintering population? James Burnham along with collaborators from the International Crane Foundation, the Kunming Institute of Zoology, and the University of Strasbourg are trying to find the answer.The reasons for the fluctuating number of Black-necked Cranes observed at Napahai are not straight forward. ‘The expansion of water and agriculture (important foraging and roosting habitat for the cranes) may have helped increase wintering numbers,’ James notes, ‘but further infrastructure development and changing patterns of agriculture may have countered these benefits and reduced Napahai’s utility for wintering Black-necked Cranes.’

A family of Black-necked Cranes and a domestic pig forage in Napahai near one of the several communities that depend on the wetland.

The size of the wetland fluctuates based on local precipitation, which changes the areas available for foraging and roosting, but other changes in the landscape are also in play. Napahai sits at the center of northwest Yunnan’s Deqen County with a population of over 130,000 individuals, predominately ethnic Tibetan and Naxi minorities. The county seat of Shangri-La, renamed in 2001 to entice tourists to this picturesque valley, sits at the edge of Napahai and its development has had dramatic impacts on Napahai.James and his colleagues are employing multiple techniques to investigate these patterns. He uses imagery from the SPOT and QuickBird satellites, which capture high resolution (down to 2.5 m pixel size) imagery to provide pictures of the entire wetland, adjacent uplands and the city of Shangri-La.

Tibetan prayer flags mark one of the overlooks of Napahai, now accessible by a new highway that encircles the wetland.

Based on these images, he is creating highly detailed maps that show the land cover composition of the area. Once those maps are completed, James and his partners will link the observed locations of Black-necked Cranes to these detailed land cover maps and identify which habitats are most important to the birds. James is also attempting to link the fine-scale satellite imagery to Landsat imagery, which does not provide as much detail as the SPOT or Quickbird satellites, but will provide more information about how Napahai has changed since the mid-1980s when economic reforms began to really transform the region. The ultimate goal is to identify how land cover has changed at Napahai, quantify the changes in foraging and roosting habitat and link those patterns with the changes observed in the numbers of Black-necked Cranes wintering in the valley. With that information, James and his colleagues might be able to piece together what is causing the decline in the valley and make concrete recommendations to local resources managers about how to limit, or even reverse, the decline of the cranes of Shangri-La.”

Recreational trails are affecting bird reproduction

Protected areas are often our front line to maintain wildlife populations, and their habitat for critical activities like feeding and breeding. But what happens when we also rely on these areas to provide recreational opportunities so that people can enjoy the great outdoors? Access and use in protected areas is on the rise and Max Henschell, a PhD student in the SILVIS lab has set out to answer the question of how recreational trails affect forest bird reproduction.

Typical Trail in Devil’s Lake State Park

Max says, ‘We are seeing more access to protected areas via trails and the concern is that this may be affecting the quality of the habitat.’ He seeks to answer some important questions. Does activity along trails affect bird community composition and reproductive success? Does size matter? To answer these questions, Max has been looking at bird reproduction in forests within the Baraboo Hills of central Wisconsin.Max has compared bird reproduction in forest with no trails with that off forest with trails. In addition to the presence of trails, he has been looking at whether the size of trails matters to these questions. He is trying to tease apart the effects of disturbance, activity that might make birds temporarily leave their nest, from habitat fragmentation, the physical break-up of large blocks of forest into smaller blocks. ‘We also want to see if there are edge effects from large trails making habitat fragmentation a compounding factor.’While Max’s research is ongoing, he has already found that trails do have an effect on bird reproduction. He says, ‘Trails definitely affect nest success. Nest success is lower, and nest parasitism and nest predation higher, in the vicinity of trails. We are also seeing that the influence of trails extends well beyond their physical footprint.’ While the results are not final, some of his findings suggest that the size of the trail matters. ‘The first season we only found 30 nests, so hopefully analysis of subsequent years with more nests will help tease apart these findings.’ Another factor he is working on incorporating is trail use. Adding that to the analysis should further help understand the effects of trails.

Parasitized Acadian flycatcher nest (Brown-headed Cowbird egg, in bottom of nest)

Trails may also affect bird community composition, but whether that is the case is not clear at the moment. ‘Identifying changes in the bird community can be really difficult because larger factors like climate variability can have overriding effects’, says Max (the two years of the study had very different weather patterns). ‘We’ve got one more field season’, he says. Here’s hoping his research concludes along happy trails.”

It is getting weirder – extreme events in satellite records

There are multiple indicators of a new climate regime, included but not limited to a changing distribution of extreme weather events. Some of these abnormalities are heat waves and severe droughts, which impose pressures on ecosystems. Jessica Gorzo is monitoring these extreme weather events in the contiguous 48 states of the United States and relating them to shifts in bird numbers and distributions.

MODIS image of land surface temperature in CA

Extreme weather events are observed when analyzing ground weather station data, but these stations exist in a limited number and therefore interpolations are needed to fill the gaps in all the areas where no stations are available. This is why Jess decided to take advantage of MODIS, which collects weather information every day from all over the world, making it ideal to observe current weather changes almost in real time.She considers this satellite data as a great advantage to obtain weather data also from areas where there is no ground weather stations to make a comprehensive analysis. MODIS has been in operation since 2002, which is also an appropriate timeframe to monitor the most recent extreme weather events.Jess is an avid birder and therefore she also wants to find the impact to bird populations caused by extreme weather regimes. She is relating the weather abnormality data with the Breeding Bird Survey to understand relationships with bird populations. She suspects there could be negative consequences of an altered regime of severe weather events, making it difficult or even impossible for bird populations to recuperate their numbers after being decimated due to weather. If the extreme events are happening back-to-back, some species could be in peril since they won’t have time to recover. Hummingbirds have been shown to be especially sensitive to drought, as they depend almost exclusively on flowers.Jess is working in conjunction with other members of the SILVIS lab including Anna Pidgeon, Volker Radeloff, Brooke Bateman-Plumb, Andrew Allstadt and Ana Maria Venegas. They are contributing in the form of weather analysis data, study of shifts in bird distributions, and avian productivity. Tom Albright from the University of Nevada (and former member of the SILVIS lab) is also providing his expertise in desert birds and dry lands climatic variation, making this a robust study.The results of this interesting work will be very useful for multiple reasons. Once the weather time series is created, it could be related with birds and other systems. Therefore it could help to explain and also predict wildlife patterns in response to climate change events. With this information land managers will be the benefit by helping them to find the areas more likely to experience weather abnormalities and allocate efforts to protect high weather sensitive species.

This is an NDVI anomaly image, displayed in grayscale, of the Channel Islands for May 2007. This image was produced by averaging May NDVI 2003-2012 per pixel and subtracting this average image from each observation to produce a difference image. This park region experienced a severe winter drought 2006-2007 that persisted into spring, and severely impacted orange-crowned warbler (Oreothlypis celata) breeding that season (Langin, et al., 2009). However, the drought and avian response differed by island, and affected oak leaf-out. Langin (et al. 2009) did not have the data to formally compare leaf-out across the islands, but measured only 34% of oaks with new leaves by April 2007 on Santa Catalina Island, compared with a qualitatively higher proportion on Santa Cruz. This is reflected in the differential NDVI anomaly values of random points chosen from the center of the islands in this image; -0.0616 below average for Santa Cruz and -0.1251 below average for Santa Catalina. Visually, you can see the darker pixels of Santa Catalina Island, as compared with the lighter pixels of Santa Cruz.