Food Quality and Vigilance Behavior in Birds

[Student names redacted]

This is an assignment I worked on as part of a group for a Behavioral Ecology class. Unfortunately we weren’t able to observe any actual birds! See our results below 😦

Abstract 

Birds are known to display vigilance behavior while foraging, though the role of food quality in vigilance levels are unknown. We observed specific vigilance behaviors at three feeders each containing a different food type: sunflower seeds, suet, and dried mealworms. No birds visited the feeders during observation times, though the food left out showed signs of being foraged throughout the week. Despite having equal access to all three food types, sunflower seeds were the food most eaten and the mealworms were barely consumed at all.  Our observations suggest a preference for sunflower seeds over dried mealworms, however no data on vigilance behavior was able to be collected.

Introduction

     Vigilance behavior in animals is traditionally understood as being a tool to keep watch for predators, though has been revealed to play an important role in the way social animals gather information about conspecific activity and available food resources (Beckoff 1995). One experiment on vigilance in birds conducted by Fernandez-Juricic, Smith, and Kaclenik (2003), investigated how social foraging species use scanning as a means to collect information about nearby individuals while feeding. Their experiments found that when barriers were placed to block vision while in head-down behaviors, birds spent more time utilizing head-up scanning behavior directed towards nearby conspecifics (Fernandez-Juricic, Smith, & Kaclenik 2003). They also found that head-up posture, which was previously thought to be the primary method of scanning in birds, is only one way birds gather visual information (Fernandez-Juricic, Smith, & Kaclenik 2003). Head-down posture while feeding is also an important aspect of vigilance in birds, and should be evaluated when studying scanning behavior in social bird-species (Fernandez-Juricic, Smith, & Kaclenik 2003). 

Another study on vigilance in birds conducted by Guy Beauchamp (2009) investigated the relationship between antipredator vigilance behavior and food density. His study on sandpipers revealed that when statistically controlling for bird density and position in the flock, looking behaviors were less frequent when in a higher density food patch, suggesting a sacrifice in safety in patches with significant foraging gains (Beauchamp 2009). Food density is positively correlated with flock size, though his research helps provide evidence to support the notion that food density could be a confounding factor in the understood relationship between vigilance and group size, and that food is a factor that can affect vigilance behaviors.

Previous research explores how birds display vigilance behavior towards competitors, and how food may impact the degree of vigilance observed. However, no previous research has been conducted on the effects of food quality on vigilance. This experiment plans to fill that gap of knowledge by investigating whether the quality of food found in the patch will affect vigilant behavior while foraging. We hypothesize that changes in food quality will cause changes in social intraspecific and interspecific vigilance and foraging behavior. We predict that birds will display increased vigilance behavior such as head-up (and head-down) posture at feeding sites that have high-quality food, and reduced vigilance and foraging behavior at feeding sites with low-quality food. 

Materials and Methods

We used three identical 11.8” round, hanging, clear dome bird feeders, three thirty-five inch shepherd hooks, five pounds of dried mealworms, five pounds black-oil sunflower seeds, twelve 11.25oz suet cakes made with rendered beef, corn, milo, wheat, millet, and sunflower seed, and an electronic balance to measure mass of food.

We placed three bird feeders in the [redacted] community garden. The feeders were initially filled with 200g seed, 200g suet, and 150g worms with one food type per feeder. We crumbled the suet before placing it in the feeder to ensure even distribution on the feeding plate and to remove food size as a variable.  The bird feeders were left out for two weeks; the first week the feeders were filled with their respective foods and left out to attract birds to and the second week was used to observe bird behavior at the feeders. We checked on the feeders multiple times in the first week and food was refilled when the feeders had little food left. On Tuesday of the second week we observed the feeders for 3 hours from the bench thirty feet from the closest feeder to record bird behavior. We created an ethogram to record behavior, as listed on the Food Quality and Vigilance Behavioral Data Collection sheet (Table 1). Each time a behavior was displayed, the behaviors were tallied on the ethogram under the section for the corresponding feeder. Some behaviors to observe include: head-up posture, head-down posture, scanning before eating, and leaving the feeder when another bird arrives. 

Results

Bird feeders in the [redacted] Community Garden were observed for 3 hours; in that period no birds were observed feeding at the feeders.  We noted that there were no birds chirping or singing in the area. If data had been collected an analysis of variance (ANOVA) would have been used to compare data points.  We observed Behaviors listed on the ethogram (Table 1) such head up posture, head down posture, multiple different birds landing on the feeder at the same time, scans before taking food, eating at the feeder, leaving with food from feeder, bird leaves when another bird arrives, and other behaviors not specified.  We recorded behaviors at the Sunflower feeder (M=0,SE=0), the mealworm feeder (M=0,SE=0), and the suet feeder (M=0,SE=0). Due to no birds being observed, major trends and statistically significant data were not able to be determined.

Discussion

Our hypothesis was that birds would display different vigilance behaviors at feeders containing food of varying values. We predicted that birds would show more vigilant behaviors at feeders containing worms, medium vigilant behaviors at suet, and the lowest vigilant behaviors at the sunflower seed feeder. Although no birds were observed at the feeders, we determined that birds preferred sunflower seeds most, then suet, and preferred mealworms least based on the amount of food left in and around feeders. These observations suggest that the high value food item is actually sunflower seeds, however the hypothesis was neither supported nor refuted because no behavioral data was observed or collected. 

There are a number of factors that could have caused birds not to forage during the observation time in this experiment. The location of the feeders could have influenced the birds from coming including the time of day relating to the proximity of a busy road, foot traffic, and other noises such as the nearby playground. The feeders were also in the middle of the garden away from trees or other protections which may have prevented the birds from foraging in the middle of the day. Lastly, the weather could have influenced the birds. The experiment was run towards the end of winter when migratory small birds may not have been present in the area yet, but the birds that were around could have been able to forage elsewhere due to the unusually warm winter and lack of snow cover and frozen ground. 

Additionally, an ornithology professor at Maine’s Colby College has noted that there has been a widespread reduction of birds at feeders in the region recently. He has stated that this may be due to declining bird populations or birds finding an abundance of food in their environment (Wilson, 2020). Further research on the subject should be conducted over a longer period of time in a location with a large bird population. For optimal observation, a camera could be utilized to view behavior at all times of the day without disturbing any of the birds.

Food Quality and Vigilance Behavioral Data Collection Sheet (Table 1)
Feeder typeBehaviorCount
Suet Multiple Birds Land on Feeder at Same Time0
Bird Scans before Taking Food0
Bird Eats at Feeder0
Bird Leaves with Food from Feeder0
Bird Leaves when Another Bird Comes0
Head-Up Posture0
Head-Down Posture0
Other Behavior not listed above0
Sunflower Seed Multiple Birds Land on Feeder at Same Time0
Bird Scans before Taking Food0
Bird Eats at Feeder0
Bird Leaves with Food from Feeder0
Bird Leaves when Another Bird Comes0
Head-Up Posture0
Head-Down Posture0
Other Behavior not listed above0
Food Quality and Vigilance Behavioral Data Collection Sheet (Table 1) Continued
MealwormMultiple Birds Land on Feeder at Same Time0
Bird Scans before Taking Food0
Bird Eats at Feeder0
Bird Leaves with Food from Feeder0
Bird Leaves when Another Bird Comes0
Head-Up Posture0
Head-Down Posture0
Other Behavior not listed above0

Table 1.  Ethogram of behaviors to observe. Bird feeders were observed for 3 hours; however, no birds visited the feeders therefore no behavioral data was collected.

References

Beauchamp, G. (2014). Antipredator vigilance decreases with food density in staging flocks of semipalmated sandpipers (Calidris pusilla). Canadian Journal of Zoology, 92(9), 785-788.

Bekoff, M. (1995). Vigilance, Flock Size, and Flock Geometry: Information Gathering by Western Evening Grosbeaks (Aves fringillidae). Ethology, 99(1-2), 150–161.

Fernandez-Juricic, E., Smith, R., and Kaclenik, A. (2003) Increasing the costs of conspecific scanning in socially foraging starlings affects vigilance and foraging behaviour.  Animal Behavior, 69, 73-81.

Wilson, H. (2020) Where are my feeder birds?  Retrieved from: https://web.colby.edu/mainebirds/2020/02/04/where-are-my-feeder-birds/

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