Effects of Temperature & Human Disturbance on Consumption of Food by Wild Birds

This topic submitted by

authors: Cindy Cohen, Justin Mccollel, and Erin Carel

cindyleigh00123@yahoo.com) at 2:09 PM on 12/14/02.

Some of our happy group at Lighthouse Cave, San Salvador, Bahamas.

Earth Systems Syllabus -Western Program-Miami University


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The Effects of Temperature and Human Disturbance on Consumption of Food by the Wild Bird Population of Southern Ohio

authors: Cindy Cohen, Justin Mccollel, and Erin Carel


INTRODUCTION

OUR HYPOTHESIS AND REASONS FOR STUDYING WILD BIRDS

Our purpose is to discover if there is any relationship between the amount of food wild birds eat and the change in temperature and habitat disturbance. We think that wild birds will eat more food as the temperature gets colder. We also believe that the birds will eat less if their feeding environment is more disturbed. We decided on this project because we were interested in how southern Ohio birds are affected by the winter months and human disturbance of their natural habitats. There is an ongoing debate among naturalists as to the pros and cons of winter wild bird feeding. We wanted to establish whether providing feeding stations helps wild bird populations or not. There are many native species such as the robin, blue jay, chickadee etc. that are partial migrators during the winter months. This means that some of these birds stay in southern Ohio for the winter and do not migrate south to warmer temperatures. Some naturalists believe these birds are only staying in this area for the winter because of bird feeders. It is a very risky winter for the birds that choose to stay by a human supplied food source. These birds become dependant on this foodduring the winter. If the food supply drops or is removed, then the birds die in large numbers. If the food supply is removed during the winter, the birds don’t even have enough body fat stored to make a late migration trip south. So, well-intentioned humans have seriously affected many types of wild bird populations by disrupting their migration instinct.
SO WHAT DO WE HOPE TO ACCOMPLISH AND WHY IS THIS INTERESTING?

This research project will be used to determine if temperature or human disturbance have an effect on the quantity of food wild birds consume. We are predicting that the colder weather will cause the birds to eat more. We believe there will be an inverse relationship between the temperature drop and the amount of birdseed our little subjects consume. This project seems logical because, at this time of year, flocks of birds begin their yearly migration to warmer temperatures for the winter. We are also curious to find out just how much food wild birds have to consume in order to prepare for the colder temperatures. Our plan is to satisfy our own personal curiosity and inform our classmates about the impact that bird feeders have on these creatures and the environment. Hopefully the rest of the class will find this subject to be just as interesting as we have. Another reason for studying wild birds is that we admire them and are fascinated with their ability to survive the harsh winter season.
We plan to try to discover just how dependant these birds become on human supplied food as the temperature drops. We would also like to find out if there is any correlation between the feeding behavior and human disturbances. This research is quite interesting because of the ongoing debate of whether we should be feeding winter birds or not. Many office parks, communities and state parks post signs during the winter months that tell the public: “Please do not feed wild birds". We believe this is wrong. It is already too late for the birds that have stayed in southern Ohio for the winter. These birds have not migrated due to human intervention, and now they will starve because people think they will go away if we don’t feed them. If we wanted wild birds to return to their natural migration cycles, then humans should have never fed them in the first place. Many people believe that if we leave nature alone, it will take care of itself. This is highly unrealistic, we do too much to affect the environment, therefore, it is much to late to practice noninterference. The birds that stay during the winter, only stay because humans have tempted them with a free meal. If we do not continue to feed them all winter, then this will be there last meal!

A NATIVE ROBIN OF SOUTHEAST OHIO

RELEVANCE

WHAT HAVE OTHER RESEARCHERS DONE??

An important study that has been done regarding this issue was conducted by the National Bird Feeding Society. It is a three-year study focused on the pluses and minuses of feeding wild birds. It details whether feeders create dependency, and how crucial these feeders have become to the survival of certain species. By supplying food for wild birds, we have caused a major habitat disturbance within certain species. The results of this study can be found at www.birdfeeding.org. Another great study was conducted by Sharon Collinage on habitat fragmentation, biological diversity, and environmental planning. This deals with the ecological consequences of habitat fragmentation and the implications for landscape architecture and planning.
Other researchers have studied birds and their eating habits in relation to their migrations. Birds need extra food to put on fat used as fuel for the journey. (Burton, 27) This illustrates the fact that birds are going to consume more resources around the time of their migration. They do this to put on extra fat for a surplus of energy. This fat surplus protects them during times of limited resource availability. Some studies have also shown that when birds have high amounts of resources that they exploit other areas of the ecosystem for energy than the areas they are accustomed to occupying. (Rappole, 28) Another theory in relation to this abundance of body fat is: when a bird has an elevated level of body fat present, then the ecosystem at the moment has a high availability of resources. If birds are in need of fat and more resources for migration, then we think there is a small correlation between migration, temperature and the food intake of avifauna. Most researchers in the field of ornithology study the ever-mysterious natural phenomenon of migration and its place in the life cycle of birds. Our project correlates to migration for the reason that it is the time of year for birds to receive their environmental cues to head to the southern parts of the United States and parts of the Caribbean. These birds will be exploiting more resources as the temperatures drop. Some of the better-known studies of birds have to do with the adaptations birds have made to fill their niche in the ecosystem. The shape of the bill on a bird has been a popular way to tell the specialization that bird species have made in order to exploit their environment. Frank Gill, a biologist, tells how the shape of the bill is the key adaptation for feeding. He also explains that the size and strength of the bill is just as important to the bird’s eating habits as its shape. Gill shows that there are only a few types of bills; there is the filter type, the seeding (present among seed eating birds), the nectar feeding (for humming birds), and the predatory (similar to a hawk’s beak). Predation has a great effect on birds eating habits as well. Birds are always on the lookout for any possible attack from predators. An example of this is given through a study conducted by Ineke T. van der Veen, in which he used a silhouette of a sparrow hawk to test the predatory reflexes of the yellowhammer. The yellowhammers became alarmed and the ones who actually saw the silhouette called out and warned the others. The witnesses returned to feeding sooner than the non-witnesses. Our experiment will undoubtedly be affected by this defensive behavior. During times of caution the specimens will, theoretically, be alertly perched and not consuming the food. Another reason that this is plausible to occur is that predators will notice that our bird feeders are getting a large amount of attention from potential prey.
SO WHY IS OUR RESEARCH IMPORTANT TO HUMAN KNOWLEDGE?

This project, like any others, has a few larger questions that are to be answered one day. The larger questions in the spotlight this time are the usual. It deals with the intelligence of animals in this way: birds will be adjusting to a new food source and then communicating it among the species adjacent to the feeding areas. With the addition of this new food source comes the threat of predators and the initial feeling of hording because the food source may be inconsistent and finite. This experiment will also deal with the question of social structure within the animal kingdoms. Some species have been known to share resources while others have been known to dominate them. This project will help shed light on the social and competitive web in Oxford and surrounding areas. Also, this procedure will illustrate the difficulty and the struggle to get an ‘edge’ within interspecies competition. A bird that finds the abundant and consistent food source year around will be the bird that is guaranteed to survive, and will have more opportunities to pass on its genes. Many species compete more within their own than with others. Due to this fact, we will have many birds of one species fighting over one food source. The advantage will go to the bird that can exploit the feeder and other resources at the same time so it does not have to rely completely on one source of food and can diversify its resources. This is assuming that the fall and winter temperatures allow growth of alternative food sources.
Unfortunately, our project will not be able to continue for the long duration that is needed to see direct results that relate habitat disruption to wild bird feeding behavior. Our research, while brief, is directly related to the larger problem of the negative impact human intervention has on the environment. We believe this research is even more important than most environmental studies, because it highlights the problems ‘well-intentioned’ home bird feeders and lovers have caused. When people think of habitat disruption they envision large factories bellowing smoke, the logging industry flattening acres of land, or the brutal slaying of natural predators. No one ever thought that a simple act of kindness, a wild bird feeder, could have caused so many problems to the wild bird population. We have inadvertently created sub species of birds that are “Kroger bird seed junkies". Our food offering is so much better than what they can scavenge from nature, that these animals have thrown away their natural migration instinct. Many southern Ohio wild bird species have become ‘partial-migrators’. This means that part of the population stays in southern Ohio throughout the winter and waits for human handouts. Non-migration spells death to hundreds of birds. They cannot complete the hundred or thousand mile trip south if they have no fat reserves built. Non-migrators are in essence more domestic than wild. When we decide we don’t want them around any longer or forget to feed them, they die. It is hard to imagine that bird food can have such an impact. This is why this research is vital to show the huge impact we have on the creatures around us!!
EXPERIMENT MATERIALS, METHODS AND DESIGN

EXPERIMENTAL DESIGN OF OUR “HIGH TECH" BIRD FEEDERS

For this project, we will be making our ‘low budget’ feeders from one-gallon plastic milk jugs. A standard measurement will then be taken with a hanging scale so that we know how much each jug weighs. The jugs will be labeled and coded correctly so that the initial measurements will be less difficult to confuse. The key issue in making the bird feeders will be in trying to squirrel proof them. A squirrel in the bird feeder will run off all the birds, and will eat most of the food on its own. This will deviate our expected results. To squirrel proof the feeders we will put an aluminum disc on the top of the feeder about one foot from the actual feeder. This disc, in theory, will prevent the squirrels from getting into the feeder so that they cannot disturb the experiment. Besides squirrels, chipmunks are also a problem with bird feeders. The aluminum disc should help prevent them from interfering with this procedure as well.
Another concern that our procedure has to account for is the disease transmission between birds. The feeders will have no sharp points or edges so that the birds are safe from open wounds that may become infected later. We also need to give the birds space. Backyard feeders are sure disease vectors, since many different flocks are attracted to feed. Under normal circumstances these flocks would have no such contact. Disease transmission is wholly prevented by normal circumstances in nature, and a feeder is not a natural occurrence. Squirrel proofing the feeders also prevents diseases because there are rodents who are carriers of avian diseases, but are not affected them selves. Replacing the food at regular intervals without letting it get bad is another good way to preserve the health of our specimens.

THE "HEAVY" ON THOSE HANGING SCALES

After weighing the empty milk jug, we will then fill the jug with commercial birdseed and obtain a weight for the seed alone. Besides the bird feeders, we will need three hanging scales. We will weigh each jug before it is filled to obtain the standard weight. After filling with seed, we will then weigh the jug again and obtain the seed weight by the ‘weighing-by-difference’ method. At the appointed times to check the jugs we will then weigh the jugs once again to obtain the new seed weight, and in this way, find how much seed was consumed. A hanging scale is ideal for this procedure because it is small and portable, thereby, quite conducive to field work.
HERE IS A PHOTO OF THE TYPE OF SCALE WE ARE TO USE


OUR MOST IMPORTANT ASSET BIRDSEED

We will also require commercial birdseed for the actual seed. We are going to be using commercial birdseed because it attracts more variety and also balances the diet for birds. The diet for birds is important because a poor diet can results in emigration, which would then have negative repercussions on the experiment. (Carey 44). Seeds offer different nutritional values, all of which birds need. For example, millet, the small, white seed, is an excellent source of starch and vitamins. Whereas, peanuts are a good source of fats and proteins. And, sunflower seeds offer a variety of nutrients and vitamins. All of these are good for birds because these help them obtain and store the energy needed to make the seasonal migration. A mix of seeds is also beneficial in that many species of birds will be attracted to them to feed instead of just a few species. This way we can obtain figures that are more representative to the entire bird population in the area at this time. We will also be using disposable cameras for the hope that we may get some good pictures of our visitors while doing periodic observation. From these pictures we can then identify some of the species we attracted with our feeders and then show our classmates what kind of birds are around during and after migration season.
METHODS- OUR EXPERIMENTAL “WAYS AND MEANS

We plan to use multiple feeders in multiple areas to obtain more representative information. These multiple areas will also be representative of different traffic areas. A few feeders will be placed in high traffic areas, a few feeders in medium traffic areas, and a few feeders in low traffic areas. The feeders will be checked a few times a week by the group and weighed. By taking the initial full weight and the check up weight we can obtain a weight for the amount of seed used with respect to the weight of the feeder. We will be checking, measuring, and recording the weights of the feeders for four weeks in order to obtain representative results. Hopefully this set up will allow us to see that in severe weather, birds will often take a chance by using a riskier food source than normal. Since it is more difficult harder for birds to travel in severe weather, they can save energy by using a closer, but not always safer food source. This careful analysis may help prove our hypothesis- that when the temperature drops the birds will consume more seed. During the routine checks of the seed weight, we will be carrying a camera with which we will try to observe some of the birds exploiting our offerings. The pictures will be used to identify the species of bird and then we can give an accurate representation of what type of birds were frequenting the feeders at this time of year (11/13/02-12/08/02). From this we can decide whether they are winter birds or partial migrators that have stayed behind to use the feeders as their main source of energy.
DATA HANDLING

Our data should be accurate because the materials we are using are simple to use and require minimum calibration. The hanging scales are simple to read and since this will be one of the only measuring device, it should not pose much of a problem. The other measuring device is a thermometer, which we are familiar with reading, so this should not be much of a problem either. The data will be kept in the same log and will be compiled regularly on a Microsoft Excel spreadsheet for organizational reasons. For the statistical area of the data handling, will be finding the mean amount of food eating per day for the mean temperature at all of the areas. This should show, on average, how much food the birds are consuming for certain temperatures. We will also be using this information to construct temperature ranges for the amount of food consumed. To illustrate our point, we could use some arbitrary measurements and say, between the temperatures of 59 -degrees Fahrenheit and 65-degrees Fahrenheit, the birds consumed eight pounds of food per day as compared to the 3 pounds per day in the temperature range of 79-degrees Fahrenheit to 85-degrees Fahrenheit. Taking all the measurements between the set ranges and finding the mean per range will obtain this. For any outlying results we will be using the Q-Test to decide whether to keep the results or to toss them out due to statistical complications. Along with the Q-Test, we will also be calculating the standard deviation and all our results will be proven to a 95% confidence level as accepted by the majority of all scientific communities. In this experiment the results should not be biased enough to have to take extra precautions in eliminating the bias. We believe the data can be trusted because of the simplicity of the measurements we are taking and simplicity of the calculations that are being performed on the data. We feel that these methods are statistically sound as a result of our past experience with data handling. We also feel that our group can handle the data very efficiently and effectively because of the simplicity of the operations at hand.
HERE IS AN EXAMPLE OF A DATA SHEET WE WILL USE IN THE FIELD


OUR TIMELINE OF DATA EXECUTION

November 13, 2002 to December 8, 2002. Unfortunately, we had to wait quite a long time to receive the hanging field scales that were vital to our recording techniques. As mentioned previously, this type of research needs to conducted over a very long period of time. The more time, the better the results will be. $$If anyone reading this would like to aid us we’d be happy to continue this research indefinitely in order to achieve more stable results!!$$ Time is the key with this project. As is the way when studying most wildlife. Persistence, patience and many years of results and data will provide the answer to the most important question: To what degree is human interference to blame for the habitat and behavioral disruption of native birds?
LETS SEE THOSE RESULTS!!!

OK, NOW LETS REVIEW THE RESULTS OF OUR PROJECT…

We plan to show our results with a series of graphs. We have created a graph for each of the nine feeders. So, each site (Mason, Oxford, Ross) will have three graphs. These graphs each depict the amount of birdseed eaten as a function of the increasing temperature. The final graph shows the functions of all nine feeders combined. We have plotted trend lines on each graph, so that one can easily see the direction that the food consumption has taken. In this way it is easier to compare the feeders and sites with each other. Also provided on each graph is an r^2 value, which is the standard deviation of the amount of seed eaten.
F.Y.I.

For the most part, Ross was intended to be our low human interference habitat, Mason was the medium environment, and Oxford was the high interference environment.

NUMBER CRUNCH- HERE ARE OUR RAW DIGITS

THIS TABLE SHOWS THE TOTAL DATA FOR ALL NINE FEEDERS


LETS SEE HOW OUR FINE FEATHERED FRIENDS FAIRED IN MASON…

GRAPH- MASON FEEDER #1 MEDIUM FOOT TRAFFIC


GRAPH- MASON FEEDER #2 MEDIUM FOOT TRAFFIC


GRAPH- MASON FEEDER #3 MEDIUM FOOT TRAFFIC


NOW LETS TAKE A LOOK AT THE OXFORD SITE…

GRAPH- OXFORD #1 LOW AUTO/FOOT TRAFFIC


GRAPH- OXFORD #2 MEDIUM AUTO/ FOOT TRAFFIC


GRAPH- OXFORD #3 HIGH AUTO/FOOT TRAFFIC


AND HOW DID OUR LITTLE FRIENDS DO AT THE FARM IN ROSS?

GRAPH- ROSS #1 LOW FOOT TRAFFIC


GRAPH- ROSS #1 LOW FOOT TRAFFIC


GRAPH- ROSS #1 LOW FOOT TRAFFIC


COMBINED DATA GRAPH- (temperature of the three sites was averaged for this graph)


Statistical tests we used:
trend line, q-test for outliers, median, and mean

DATA REVIEW, DISCUSSION AND CONCLUSIONS

Overall, at each site (Ross, Oxford and Mason) we observed these types of birds feeding at least once: robins, blue jays, Carolina chickadees, house finches, mockingbirds, cardinals, and house sparrows. The majority of the birds seen at each site were robins and blue jays. This is not surprising, for their size these tend to be quite aggressive birds. Blue jays are well known to chase off much larger birds, cats, dogs and even people! This blue jay behavior was observed at the feeders in Mason where Cindy’s dog max has a continuous battle raging with these creatures. Having done something to offend them, he is now the subject of kamakazee blue-jays and has even caught and eaten a few! It is a common site to see a blue jay chasing and tormenting a much larger hawk or crow. Blue jays are extremely territorial, and will fly at the threatening party while screeching very loudly. We suspect that the blue jays dominated the feeders, and chased many other birds away.

CINDY’S CRAZY DOG MAXWELL


PICTURE OF A BAD BLUE JAY- DON’T MESS WITH THIS!

Our research data shows that the overall trend was for more seed to be consumed during warm warmer temperatures. This is directly contradictory to our hypothesis! All our feeders were frequented more during warm weather. But, human activity level did make a difference in the amount of food consumed for each feeder location. We observed wild birds frequenting the feeders that did not have much interference in from the direct environment. The Ross site (low activity feeders) was over run by blue jays and robins, whereas the Oxford site (high activity feeders) was not frequented as much. Also, feeders that kept the individuals more protected and less visible to predators were the most popular. The feeders that were in the open were among the least popular.
The mean temperature for the Mason site was 38.9 Fahrenheit, and the mean amount of food eaten during the interval was 1.00 pounds. For the Oxford site the mean temperature was 44.9 Fahrenheit, and the mean amount of food eaten during the interval was 0.66 pounds. And, for the Ross site the mean temperature during the testing interval was 38.8 Fahrenheit, and the mean amount of food eaten during the interval was 1.53 pounds. The means for food consumed were obtained by averaging the three feeders at each site. The trend lines for each of the nine feeders show a positive correlation between increased food consumption and increased temperature. There was outliers that should be eliminated for failure to pass the q-test found on Ross Feeder #1 graph. We still included this point when zero food was consumed on November24. Our reasoning is that no food was consumed on that date due to human disruption of this feeder, which we are attempting to link with this study to begin with.
There are many possible explanations for the trends that we discovered. The temperatures during our study time may not have dropped enough, or there was not enough temperature variation. It was unseasonably warm in southern Ohio during the period of testing November 13, 2002 to December 9, 2002. The native birds may have preferred the native seeds and berries that were available due to this warming trend. The duration of our study was simply not long enough. Had we gone all winter we may have seen birds eat more as the temperature dropped. Perhaps, not many of the wild populations had migrated yet, due again to the delayed winter. Or, as the temperature dropped, the birds migrated en masse, leaving less birds to

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