The Nutritional Ecology of Bird Migration

 

I attended a lecture by Dr. Susan Smith on her research related to migrating birds and berry nutrition. Migratory birds spend up to four months a year in the process of migration. These migrations are to wintering grounds and breeding grounds. During these trips, physiological demands are much greater. These trips require very large energy reserves. 79 percent of these reserves come from fats.

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These stores of energy are depleted and then restored at migratory stopovers. At these sites, refueling occurs. This must be rapidly done due to time constraints (must get to wintering ground before winter). Bird’s diets change during migration to be able to rapidly refuel. Birds eat large amounts of fruit. The benefits of eating fruit in place of their normal diet are fruit is high in fat and fruit is easier to hunt. There are limits birds have to eating fruit. One type of limitations are digestive. Bird’s digestive systems can only handle a certain amount of seed load. Also, some fruits contain a certain amount of toxins and the system can handle only so much. Other limitations are nutritional.

Fruit varies in energy and protein content. Some contain up to 40 percent fat, most of these include native species. As fat content increases, energy density also increases. A hermit thrush (Catharus guttatus) (that on average weighs 31.2 grams) would have to eat 18.8 grams of bayberry (Myrica sp.) (high in fat) or 90.7 grams of pokeweed (Phytolacca decandra) to fill the daily energy needs. Eating this much pokeweed is clearly not possible.

 

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A hermit thrush (Catharus guttatus)

 

One of Dr. Smith’s studies tried to see if birds prefer certain fruits during autumn migration time. Nets were placed around berry bushes and the amount that natural falls off was measured. The nets were removed and the amount of berries eaten during different times of the year was measured. The amount of arrowwood (Viburnum dentatum) (high in fat) eaten increased during migration, were as the amount of chokeberry (Aronia sp.) (low in fat) eaten stayed the same.

Another study was done by Dr. Smith using the plasma metabolic profile (blood samples). These samples provide information on metabolic fuel use and energetic condition. Lipid metabolites indicate how mass has changed over the last several hours (showing refueling). Other metabolites provide more information. Plasma was also sampled at two different stopover sites to compare them.

These sits were the Braddock Bay Bird Observatory and Rochester Institute of Technology Bird Observatory. At Bradock Bay Bird Observatory there was 200% more ripe fruit and this was 83% native berries (tend to be higher energy). At Rochester Institute of Technology, there were only 10% native berries. Birds were sampled the same day and same time at these locations. It was found that at Braddock Bay Bird Observatory those birds had higher triglyceride levels. This proves that fruit is helpful in birds refueling.

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Dr. Smith hopes to continue in researching the effects of fruit on birds. One study she wants to do is compare seasonal and site differences in fruits nutritional content. She also wants to look at if the bushes that provide fruit provide a year round value (such as a place to nest in or find insects). She wants to develop fruit fingers prints (light that comes off fruit when you shine a fluorescent light on it). This can be used to quickly tell if a fruit has high or low nutrients. Lastly, Dr. Smith wants to see if invasive species are so integrated into the system that removing then would cause harm to bird by removing a food source.

Vegetation Sampling

The following is adapted from a vegetation sampling lab I did in college.

INTRODUCTION

In order to properly study an area, one has to know certain characteristics of that area. Studying the vegetation of an area has its many benefits. These include allowing us to understand the difference between communities, describe habitat, and understand how vegetation reacts to certain environmental gradients. In this lab, we focused on using the point-centered quarter method to characterize a forested slope.

From the data collected we can calculate average density per hectare, relative density, density, basal area, relative basal area, frequency, relative frequency, importance value, and relative importance value. These values allow us to compare characteristics among different species. This was the main objective of this lab.

METHODS

This study took place on Pine Hill Alfred, NY on September 9th, 2013. Following the gas pipeline trail behinds Ann’s House on the bearing N10Wo we walked 5 meters off the gas pipeline trail. At that point we placed the center of a quadrant composed of 90o quarters. Quarters 1 and 2 faced North, 1 being on the East side. Quarters 3 and 4 faced South, with 3 being on the East side. We determined the four closest trees to the quadrant, with a diameter at breast height over 10 cm. For each tree we calculated the distance from the quadrant, diameter at breast height, and the tree’s species. The same process was repeated for a quadrate located 25 meters from the path.

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Phase I environmental site assessment (ESA)

In the field of environmental consulting conducting Phase I environmental site assessments (or ESA) is very common. This is often the 1st phase in environmental due diligence. The EPA sets the standards in which this process is carried out. The report basically outlines if there is any potential environmental contamination at a site because those who own the property are responsible for it under federal Superfund law. In response to Love Canal, in which was a massive environmental disaster in Upstate New York, the government passed the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) in 1980.  This act forced the clean up of industrial waste sites and made the owners responsible for waste on their property. COnducting an ESA ensures that property owners are protected from this liability. These reports are typically done when a commercial or industrial property purchased to ensure that the buyer is not receiving an environmental disaster that will be very costly to fix. A Phase I ESA may be required from lenders, local banks, or municipalities. They may also be required when applying for a building permit, there is a change in ownership or zoning laws are changing. Sampling of air, groundwater, and soil is not conducted during a phase I ESA. This type of sampling is included in a Phase II ESA which is done if it is evidence of environmental contamination.

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How will climate change and impact Chytridiomycosis and amphibians?

Chytridiomycosis is a disease that is killing amphibians worldwide at alarming rates. To read more about amphibians see this blog post. The disease is caused by Batrachochytrium dendrobatidis or Bd for short. Bd is a fungus that is specific to amphibians. Currently, the disease is responsible for the greatest disease-caused loss of biodiversity in recorded history. Species have had massive drops in populations and seem to have disappeared overnight.Bd occurs inside the cells of the outer skin layer. It causes microscopic changes in the skin and enlarges this layer. This is deadly because amphibians absorb water and salts through the skin. In the family of lungless salamanders, and one lungless species of caecilian Bd causes them to suffocate. Bd travels into the mouthparts of tadpoles or other larval amphibians. When tadpoles change into adults the infection spreads to the skin. Spores, which are the reproductive part of the fungus, cause the skin to become enlarged. This reduces osmotic regulation and electrolyte blood levels drop which leads to cardiac arrest. Chytridiomycosis has almost a 100 percent mortality rate.

 

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Cells infected with Batrachochytrium dendrobatidis 

 

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R and K selected species

R-selected and K-selected species are terms that biologist use to describe the reproductive strategy of animals. Either an animal produces a large number of offspring and it basically is a numbers game for those offspring or the animals have few offspring and invest a large amount of time in those offspring. R-selected species are those that favor a large number of offspring. This includes animals like insects, amphibians, many fish, and reptiles. They tend to be smaller organisms so the energy used to make each individual is low and live in environments that are unstable. They also have shorter lifespans and reach sexual maturity quickly. They have type III survivorship pattern which means that earlier in life more organisms will die than later on in their life. In these species, the number of offspring is important because it directly impacts the population size.

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Lupines and butterflies; a failed project

The summer after my 1st year of college I did a somewhat misguided ecology project related to the Karner Blue Butterfly (Plebejus melissa samuelis). The butterfly larvae only feed on wild lupines (Lupinus perennis). As lupines are early successional plants, as the Northeast transitions back into the forested lands it was before European colonization, the lupine populations are also shrinking. With those populations, the butterflies are dying out. When the butterfly was listed in 1992, 99% percent of its population was already gone. It used to be found from Minnesota to Maine, which included my home state of Vermont. Now the butterfly can only be found in Minnesota, Wisconsin, Indiana, Michigan, New York, New Hampshire, and Ohio, although reintroductions have occurred in 3 other locations. I did not do as much research about the butterfly as I should have in the planning stage of my project but we will get to that later and hopefully, this can serve as a lesson to you as well in planning future projects.

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Blue lupines (Lupinus perennis) are now endangered in the state of Vermont according to the Natural Resources Conservation Service. They have a taproot that helps to stabilize areas to prevent erosion. Since they serve as host plants and were easy to find the seeds for I bought 16,000 seeds on Amazon. I took the seeds and made them into what are called seed bombs. Seed bombs were created during the Guerrilla gardening movement, people would use them to plant flowers in empty lots that they could not otherwise access. It is basically a ball of mud, seeds, and fertilizer that you are able to throw. Here is more information on seed bombs. It is important to keep in mind what plants are native and which plants are not. I used two seeds per seed bombs because cross-pollinating lupines plants produce more seeds than those who self-pollinate. The fertilizer used was made from natural plant products, because it doesn’t raise nitrogen levels if washed in a waterway.

 

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Some of my many seed bombs

 

The Karner Blue butterfly is only an inch wide and has very limited dispersal, an average of 1000 feet. IF I had done more research I would have figured out that planting lupines where the butterfly does not exist, literally serves no benefit to it. At the time since Vermont is in the historical range, I thought that one of the butterflies would make its way to my lupines. This project lacked practicality and enough background research. I also had no taken outbreeding depression into account when I bought random seeds on Amazon. Outbreeding depression occurs when you breed two populations that wouldn’t have breed together in the past together. The result is lower genetic diversity in the species.