Foraging Birds

Foraging in birds is controlled by the risk of predation and starvation. Consideration of the energy required maintaining flight and body metabolism plays a significant role in forage selection, habitat choice, and feeding time. Although many studies have explored the optimal energy reserves and the risk to predation and starvation, few studies have accessed the daily feeding pattern and progress of feeding in birds. The study was therefore intended to investigate the daily foraging pattern of passerine birds in Schmeeckle Reserve of UWSP and provide supportive evidence for the studies. The study employed the observational research design and supplemental feeding to collect the data. From the 530 visits recorded, the study found out that birds in Schmeeckle Reserve like to feed continuously from the morning to the afternoon at an increasing rate then decrease towards the evening. The results of the study supported the relative constant activity theorem i.e. birds forage continuously throughout the day over the bimodality prediction i.e. birds prefer to feed early in the morning or late in the evening.

Introduction

The foraging behavior in birds is controlled by the risk to predation and energy consideration (Bonter, Zuckerberg, Sedgwick, & Hochachka, 2013). Birds develop adaptation to obtain energy from the environment while reducing the likelihood of predation by other birds (raptors), mammals or reptiles. Flying is the process that require much energies (Maina, 2000). Therefore, birds with low-fat levels (reserve) in their body increase the risk of starvation that may lead to high mortality (McNamara, Barta, Houston, & Race, 2005). The likelihood of predation and starvation causes birds to have a preference in the food taken, feeding area and feeding time (Bonter et al., 2013). It is, therefore, important to understand foraging behaviors in terms of pattern of feeding, as well as the risk associated with these behaviors.

Risk to predation and risk to starvation have conflicting effects on the optimal energy reserves in birds (Pravosudov & Lucas, 2001). Many studies have, therefore, assumed a balance of the two risks while investigating the foraging patterns in birds (Bonter et al., 2013). Perceived likelihood of predation can reduce the foraging success of birds. A recent study has shown that competition causes birds to be more vigilant than feeding which has an effect on the energy reserve (Peck, Pringle, Marshall, Owens, & Lord, 2014). Other studies have concluded that the risk of predation leads to temporal changes in the foraging behaviors of birds, especially reducing the feeding time. Consequently, it leads to danger of starvation due to low energy reserve (as cited in Bonter et al., 2013).

Although it is essential for birds to enhance their energy reserves, fat gain increases the risk of predation. This is because fats reduce the flight muscle power and, therefore, affect the efficiency in flight (McNamara et al., 2005). High-fat level is also believed to increase the body metabolism hence birds with more fat tend to forage a lot increasing risk to predation.

While many studies have examined the likelihood of predation, starvation, and optimal energy reserves, few studies have been conducted to assess the daily foraging patterns in birds (Bonter et al., 2013). Ainley and Ballard (2011) conclude that penguins prefer to forage at night to reduce the chances of being spotted by a predator. Bonter et al. (2013) conclude that birds prefer to forage constantly throughout the day from sunrise to sunset other than feeding more at dawn and dusk. McNamara et al. (2005) and Pravosudov and Lucas (2001) argue that birds prefer to feed early in the morning before sunrise and at dusk.

Even with the few studies on feeding pattern, limited research has been done to indicate the progress on a daily foraging pattern through-out the day. Brittingham (1992) concludes that the Black-Capped Chickadee visit a feeder at an increasing rate throughout the day (as cited in Bonter et al., 2013). However, a study by Van der Veen (2000) on Yellowhammers show an opposite pattern of feeding pattern i.e. visits of the Yellowhammer to the feeder(s) reduce throughout the day. This study was, therefore, intended to provide supportive evidence on the feeding pattern and progress of foraging patterns throughout the day in granivorous (seed-eating) birds.

The feeding pattern of Passerine birds was investigated by observing the number of visits to a feeder at dawn, afternoon and dusk. With the help of the binoculars and a timer, the birds’ foraging success was examined, i.e. the number of seeds took and time spent at the feeder. The objective of the study was to investigate the preferred feeding time of passerine birds in Schmeeckle Reserve of University of Wisconsin-Stevens Point (UWSP). The hypotheses of the study were: (1) there is no preference on the time of day that bird species forage in Schmeeckle Reserve. (2) There is no relationship between the time spent by a bird at the feeder and the number of seeds taken. There were a couple of predictions for the study; prediction 1: Species of birds would prefer to eat in the morning due to predators being less active in Schmeeckle Reserve. Prediction 2: Birds would prefer to eat in the evening because they would be less visible to predators in Schmeeckle Reserve.

Material and Methods

I studied the feeding patterns of several birds’ species in the order Passeriformes at Schmeeckle Reserve of UWSP. The study employed the observational research design, i.e. birds were observed from a hiding position, where the species, the number of seeds taken and time spent at the feeder by each bird were recorded. The study was conducted at Schmeeckle Reserve in UWSP, USA. The studies area is Conservancy, covering 280 acres. The Reserve is a wildlife refuge for the natural communities of central Wisconsin, a recreation center and an outdoor laboratory for learning. It is characterized by diversity of ecosystems, since it is an ecotone for the northern and southern habitats. It inhabits over 200 species of birds, as well as mammals, reptiles, and amphibians. The ecosystem selected for the study was the terrestrial Berald Oak Savannah. It offered a good site for viewing the birds, as well as setting the feeding station. One feeding station which had been placed two weeks prior to the data collection for habituation (Peck et al., 2014) was used during the study.

Experimental Procedure

A squirrel-proof feeder (Brome 1015 Squirrel Buster Classic) was placed on the selected feeding ground at the Berald Oak Savannah. It was observed that Schmeeckle Reserve is home to the flying squirrels, hence the consideration of a feeder which is squirrel proof. It was placed above the ground to enhance visualization because the target group consisted of perching birds. Sunflower seeds and peanuts were provided in the feeder, since they are preferred by passerines and are known to be energy producing foods (Bonter et al., 2013). Observations were made using binoculars to enhance vision of the pecking rate and identification. Birds guide books were used to help in identifying common names of the visiting birds. A timer (stopwatch) was used to record the time each bird spent at the feeder.

Data Collection

Data was collected in four days and foraging pattern on the artificial feeder was recorded by observations made in the morning (6-8 am), afternoon (12-2 pm) and at dusk (4-6 pm). Birds’ species visiting the feeder were recorded in a table that consisted of various columns. The common names, time of the day, sex (if identifiable), number of seeds taken and time spent at the feeder columns. Using a pair of binoculars for viewing and guide book for identification, bird species visiting the feeder and the pecking rates were recorded. The time spent at the feeder was measured using a stopwatch from the time the bird arrived to the time when the bird left the feeder. The sex of the birds was only provided to the birds whose sexual dimorphism was easily identified with the time frame, e.g. sparrows.

Data Analysis

Data collected on the foraging pattern was analyzed using descriptive statistics (frequency and percentage). Analysis of variance (ANOVA) was used to test the difference between the average birds’ species visiting the feeder at different times of the day (morning, afternoon and at dusk). The data was grouped in three categories in terms of time of the day. Birds’ species recorded in each class were tabulated (Table 1). The data in the table was used to calculate ANOVA in Minitab. Correlation analysis was done in Minitab to investigate the relationship between the number of seeds taken by a bird and the time spent at the feeder. The analysis could help us understand the foraging success of each bird.

Results

Over the three-time frames, 530 feeder visits were recorded without taking into account repeats. 166 visits took place in the morning, representing 31.3% of the total visits. The afternoon recorded the largest number of visits (301), representing 56.8% of the total number of visits. The lowest number of visits were recorded at dusk, with only 63 visits, representing 11.9% of the total (Table 1). Of the total visits, 366 (69%) visits were by the Black-Capped Chickadee, 71 (13.4%) by the Red-Breasted Nuthatch and 64 (12.1%) by the white-Breasted Nuthatch. Small number of other birds 29 (5.5%) were recorded, e.g. the blue jays, etc. (Table 1). Visits were dominated by the Black-Capped Chickadee.

Table 1. Number and percentage of feeder visits by different birds’ species in the morning, afternoon and at dusk

The analysis of variance (ANOVA) indicated that there was no significant difference between the mean birds species visitations (F (2, 15)

Discussion

The results on the progress of foraging patterns (percent of totals) indicated that foraging gradually increases from morning to afternoon, and reduces towards the evening. The ANOVA results showed that we should not reject the hypothesis and that there was no preference on the time of day that bird species forage in Schmeeckle Reserve. These results showed that birds at Schmeeckle Reserve had no preferred time to eat. The reason could be the supplemental food offered, secure feeding grounds with reduced predation risks and energy to search for food. Number of seeds taken positively correlated with time spent at the feeder. It, therefore, indicated that an increase in the time spent at the feeder resulted in increased number of seeds taken. This helped to understand that birds at Schmeeckle Reserve succeeded in foraging and that they engaged in feeding more than vigilance. Upon arrival at the feeder, birds spent more time picking the seeds than being vigilant.

The study supported Bonter et al. (2013) conclusion that daily feeding pattern predicts more of the risk-spreading theorem than the bimodal foraging pattern. It also supported the conclusion that the foraging success in birds is attributed to the time spent at the feeder (Peck et al., 2014). Less vigilance increased the rate of pecking, and, therefore, the study supported Pascual and Senar (2013) conclusion that the pecking rate reduces with increase in vigilance, resulting from increased risk of predation and competition.

The study partially supported Brittingham’s (1992) research that the Black-Capped Chickadee visited a feeder at an increasing rate throughout the day. The current study showed that at Schmeeckle Reserve increased from morning to afternoon and then decreased towards dusk. The opposite pattern (decrease) partially supported the research on Yellowhammer in Sweden by Van der Veen (2000) (as cited on Bonter et al., 2013)

The results, however, conflict with Ballards’ (2011) conclusion that birds (penguins) preferred to be fed at night to reduce being spotted by predators. Also, it did not support McNamara et al. (2005), and Pravosudov and Lucas (2001) proposed hypothesis that birds prefer to eat in the morning and evening, i.e. the early and late peaks (bimodality).

You can ask us “write my descriptive essay” on this or any other topic at 123HelpMe.org. Don’t waste your time, order now!

In summary, the study showed that passerine birds foraging pattern at Schmeeckle Reserve supported the relative constant activity throughout the day, rather than preference to eat at the early or late peaks (dawn and dusk). It also indicated that birds in the reserve tend to a mixed progress in the foraging pattern with an increase registered from morning to afternoon and a decrease from afternoon to dusk.

The study could provide information on the foraging behavior and patterns of artificial birds’ feedings. This information could be essential in providing ideas and rationale to researchers, intending to explore birds’ foraging, especially in natural setting. The drawback of the study was the use of artificial mode of feeding that could have altered the natural foraging behavior, hence resulting in biased results. Further studies should be performed in birds’ natural setting to investigate the effect of predation on feeding time preference.

Acknowledgement

I am grateful to God for giving me an opportunity to perform the study. I also thank the Schmeeckle Reserve management for allowing me to use the Reserve for data collection. I also acknowledge my colleagues, particularly, Abby, Antony, Angel, Ashley, Whitney and Courtney for their support and assistance in data collection. I thank everybody who contributed in some way to this research.