A Study of the Influence of Food Handling Time on Bird Foraging Behavior in Ontario

A Study of the Influence of Food Handling Time on Bird Foraging Behavior in Ontario

Introduction

Bird species inhabit a wide range of environments and as such they must exploit different approaches to food acquisition. In Eastern Ontario, as temperature drop below freezing, the food availability declines significantly resulting in some species of birds migrating in the winter to take advantage of the plentiful food resources in the South. Other bird species, however, do not migrate and have developed behaviors that allow them to survive Canadian winters where food is scarcer. Behavioral ecology focuses on the evolutionary mechanisms that act on animal behavior due to pressures from the ecological system (Bonter, Zuckerberg, Sedgwick, & Hochachka, 2013).

The search for food for survival is an intrinsic need that has to be satisfied and birds are not an exception when it comes to survival (Kacelnik et al.1981). The presence of food is not just a surety that the birds will come to forage but rather, there are combinations of factors that determine whether a bird will land and take the food that is available (Yahnke, 2006). The factors that determine the foraging behavior include the distance from the central point where the bird originates, the time taken to access the food, and the predatory risk as the bird forages for food (Yahnke, 2006).

Among the factors that determine the foraging habits of birds is the temperature and environment in which the bird lives. When the temperatures are extremely low, the birds tend to migrate while others remain to adapt to the change in weather patterns. The adaptation comes with the sharp insight into the factors that determine the foraging patterns of the birds. The Optimal Foraging Theory thus comes into play when there is a bid to get food in the most energetically feasible manner.

Foraging theory is a branch of behavioral ecology that deals with the behavior associated with searching for and exploiting food resources with respect to the environment that the organism lives. One such model for studying these behaviors is the Optimal Foraging Theory which suggests that while foraging an organism will adapt a strategy that maximizes energetic returns while minimizing energetic costs and risk of predation. This experiment aims to explore how bird foraging behavior of the bird species within the Marshlands Conservation area in Kingston, Ontario, is influenced by food handling time.

Background

Food is a crucial requirement in the life of every animal in the planet. In every ecosystem the animals tend to forage for food depending on the risks within the ecosystem and the nature of the food. The Optimal Foraging Theory is the best in explaining the patterns that are observed in animals that seek out to capture prey in the ecosystem. In the real world of humans the theory can be explained using the example of children given the choice of doing a trick-or-treat in a neighborhood that has houses close together or in a neighborhood that has the homes wide apart. The children most definitely choose the homes that are closer together that give them the chance to collect more treats.

Birds tend to forage on foods using different methods and these methods depend on the length and type of bill, the dietary preferences, and the distance covered to reach the food. The types of foraging that are common include scratching that is done using the foot or in other cases both feet of the bird to get to the seeds or insects. The other type of foraging is gleaning in which the bird carefully looks for the insects or seeds for nutrition. The third type is hawking in which to catch insects, the bird snatches the insect in the air and sparrows are commonly known for this method of foraging.

The fourth type of foraging is scanning that requires sharp eyesight and raptors are known for this type of foraging. Sallying on the other hand involved the capture of insects in flight and then perching on a surface for eating. Diving is commonly observed in penguins and loons to capture fish and other under water animals for food.

The issue of time is another factor that needs to be put into consideration by birds that seek to get food in the most effective manner possible. At the same time, we can correlate time and the distance that is covered from one point to another to get the food. When the distance is long, there tends to be more time that is spent looking for the food and the birds will not choose to forage in places that are distant. The energy taken to get to the food and the energy value are all high and not worth the cost of covering the long distance.

In relation to time, if it takes a longer time for the birds to get the food ready, there tends to be the risks that the bird is exposed to such as other predators that seek out to capture the birds for nutritional value. The presence of predators in the environment where one animal searches for food implies that there are higher chances that the animal will be captured. As a result, there tends to be a leaning towards environments that are more concealed and can provide cover for the animal, in our case birds.

The size of the food also plays a major role in the foraging patterns of the birds. The Optimal Foraging Theory posits that the birds will tend to go for the food that has the most energy value and low risk. When the Optimal Foraging Theory is considered, the food that has the larger size is the most preferable (Lima, 1986).. However, in some cases, this tends to be false as the birds opt for smaller pieces of food that are easily eaten and flown around to their nests. When the food is small, the time taken to eat the food or to even transport the food is cut by a large proportion, making survival possible.

A study showed that crabs preferred smaller pieces of food over large pieces. In the same manner that the animals prefer to take smaller pieces of food (Lima, 1986)., the preference of stationary prey over those that are on the move is evident and further proves the validity of the Optimal Forage Theory. The preys that are stationary tend to be much easy to capture then those that are mobile. The mobile preys tend to make the predator to expend a lot of energy chasing after them and also much time that would otherwise be used gathering other more feasible prey (Olsson et al., 2000).

Much research has been done into the behavioral ecology of animals and their foraging habits. Many factors go into the considerations of what prey to pursue and the kind of environment the prey resides. The forager thus has to have a sophisticated level of fitness that enables them to hunt and capture their prey for food. The aim is t always take lesser time and achieve high energy gains.

Application of the Experiment

The experiments that have been used to investigate the handling time of food by the foragers proved that the birds that forage on these foods on feeders are usually small. The small birds are endotherms that when exposed to the cooler temperatures of the night, tend to expend a lot of energy, thereby making them forage more lest they succumb to hunger. The study is thus favorable for the study of birds in Ontario, Canada, given the likelihood of these birds remaining in their habitat even during the winter season. There has been no other study that has been done on the birds in Ontario, studying their food handling. An understanding of their behavior will enable students in academia to understand the Optimal Foraging Theory better.

Purpose of this Study

The purpose of this study is to understand the feeding habits of the birds in Ontario. The relationship between the nature of the food and the depth of the feeder food that remains after foraging is the main aim of this study. The study aims to establish the relationship between the two and compare the findings with the Optimal Foraging Theory. Optimal foraging theory predicts that animals will select the foraging strategy with the greatest net energetic return. Thus, various factors are predicted to influence foraging behavior, including the energy content of a food source, the handling time required to collect and consume the food item, and the predation risk associated with foraging. The Optimal Foraging Theory has been found to hold true for many animals such as the crabs that prefer to eat smaller foods compared to larger ones that would take longer to consume, lowering their chances at survival in a harsh environment. The Optimal Foraging Theory is applicable as it enables animals to feed in habitats without formidable challenges to their diet and survival.

Hypotheses

Research question: Does food handling time influence foraging behaviors in birds in Eastern Ontario?

The hypotheses that are to be applied to answer the research question in this study posit that the birds will favor foraging strategies that minimize their food handling time when all other factors remain constant (H1)

• H1: birds prefer hulled seeds
• H2: birds prefer intact seeds
• H0: birds show no preference in seed choice

The study aims to prove hypothesis (H1) or have the hypothesis disproved, meaning that it will be contrary to the Optimal Foraging Theory. In the event that the hypothesis (H1) is upheld, it may explain the reason as to why some of the birds remain during the winter when other bird species fly away to farther lands, which is a contradiction of the optimal Forager Theory.

Methods

One week prior to each date of data collection two bird feeders of identical size, shape, number of perches, and approximate distance from the ground were paired and placed, with permission, at randomly chosen locations along the Rideau Trail. This was to allow the birds to locate the feeders and habituate to feeding at them. For each trial, one of the feeders was assigned the treatment of being filled with intact sunflower seeds while the other was filled using hulled sunflower seeds.  Both feeders were placed in close proximity to each other on the trail to control for factors such as canopy cover, weather, and species present. The feeders were filled with their respective seeds two days prior to data collection. The seed depletion for both of the feeders was then measured by recording the reduction in seeds from the top of the feeder to the leveled seeds that remain as a measure of food consumption. The bird feeders were both equipped with measurement units directly on the feeder to alleviate any discrepancies between measurement devices.

Statistical Analyses

The statistical tools that were used for this study sought to establish the preference of one food over another. In this study, it was to be established the preference of the birds to eat the hulled seeds over the intact seeds. As a result, the tables needed for the study were prepared from the data that was in Excel spreadsheet and then graphs drawn to give the output. The following are the tables and the graph that was obtained:

Figure One: A table of the hulled and the intact seeds and their depths (centimeters).

Results and Discussion

Figure three: A graph showing the trend of the preference of food (hulled or intact).

A simple graph was drawn from the data given on the preference for the hulled or the intact seeds. The trend of the curve show that in the first three quarter of the graph area, a preference for the hulled seeds is evident as the curve is above the one that is for the intact seeds. The implication is that the Optimal Foraging Theory holds true for the birds in Ontario. The birds remained during the winter and thus had to adopt survival mechanisms that favor such an environment. The time taken to eat hulled seeds is less than that which would have been used to eat the intact seeds.

The hulled seeds take a lesser time due to the accessibility of the food directly with little expenditure of energy by the birds (Brown, 1988). At the same time, there are other factors that contribute to the trend that has been observed. The first is that extrinsic factors contributed to the trend that has been obtained. The seasonality of the preference of one food over the other is due to the cold season (Lima, 1986). Since the food was in the feeders, the birds that tend to prefer this mode of feeding are mostly endotherms (Sih and Christensen, 2001). The endotherms tend to consume a lot of energy either at night when the temperatures are low, or during the cold winter season. As a result of this extrinsic factor, the Optimal Foraging Theory holds true for the birds in Ontario.

Birds are animals that are small in size and this smallness makes them difficult to observe in studies such as this one (Lima, 1986). The choice of using feeders is the best strategy in such a setting as it enables the researchers to note the depth of the feeders as an indicator of the preference of one food over the other to establish their foraging habits. Such a research is thus tedious and requires agility and adaptation on the part of the researcher.

The masses of the seeds that were used in this study were similar, regardless of their type. The type of the seed is determined by whether they are hulled or intact. Research has proven that the masses of the seeds are similar and therefore there has been no disparity between the type of seed and the depth that was observed. The difference in the depth is indicative of the costs that were undertaken to obtain the food.

Implications of the Study

The study on the preference of the birds in Ontario to eat the hulled seeds over the intact seeds will serve as evidence in a theory class that they theory is true. The study offers a testing ground for the theories in ecological studies and thus adds a practical dimension to the studies on ecological behavior. The conclusion is that the birds remained true to the Optimal Foraging Theory by reliance on the resources that were readily available to them in the kind of environment they were exposed to, the proximity to the food source, and the risks they ran when looking for food.

References

Bonter, D. N., Zuckerberg, B., Sedgwick, C. W., & Hochachka, W. M. (2013). Daily foraging patterns in free‐living birds: Exploring the predation‐starvation trade‐off. Proceedings of the Royal Society B: Biological Sciences, 280, 20123087.

Brown, J.S. (1988). Patch use as an indicator of habitat preference, predation risk, and competition. Behavioral Ecology and Sociobiology, 22, 37–47.

Kacelnik A, Houston AI, Krebs JR (1981). Optimal foraging and territorial defense in the great tit ( Parus major ). Behav Ecol Sociobiol, 8:35–40.

Lima, S.l. (1986). Predation risk and unpredictable feeding conditions: determinants of body mass in birds. Ecology, 67, 377–385.

Olsson, O., Wiktander, U. & Nilsson, S.g. (2000). Daily foraging and feeding effort of a small bird feeding on a predictable resource. Proceedings of the Royal Society of London, Series B, 267, 1457–1461.

Sih, A. & Christensen, B. (2001). Optimal diet theory: when does it work, and when and why does it fail? Animal Behavior, 61, 379–390.

Yahnke, C.J. (2006). Testing optimal foraging theory using bird predation on goldenrod galls. American Biology Teacher, 68, 471–475.

https://docs.google.com/spreadsheets/d/189FAo8h4bznejc9We6JhtLqRISW9jxMCz-

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