Pelican Behavior

Pelican Behavior on Wee Wee Cay, Belize 03/06/09 Laura Outlaw, Jessie Poole, Callie Turlington, Olivia Wiggins

Abstract: Wee Wee Cay is a newly found habitat for brown pelicans (Pelecanus occidentalis). The pelican’s old habitat, Pelican Island, was destroyed so the pelicans recently found a new home on

Wee Wee Cay. In our experiment, we analyzed the pelicans’ behavior by determining their preferred side of the island and their preferred feeding times. We did this by measuring the concentration and intensity of bird droppings on the mangrove leaves and by measuring their rates of diving throughout different times during the day. These measurements led us to find that the pelicans prefer to inhabit the lee-ward side of the island and that they prefer to feed between 5:00-6:00PM. We also discovered the since the prime source of food for the brown pelican is minnows, and that the pelicans behavior directly correlates to the minnows behavior.

Introduction: While reviewing possible research topics in Belize, we decided to focus on birds since little NCSSM student research had focused on birds previously. Our observations were based off the Brown Pelicans (Pelecanus occidentalis) that inhabit on Wee WeeCay. There are over 100 mangrove cays in the Caribbean coast of Belize, Central America. Wee Wee Cay is at point 16°46’ N, 88°08’ W, which is a single isolated cay over 5km from the mainland shore and over 2 acres in area (Elisonand Farnsworth, 1996). The Brown Pelicans are a relatively new addition to the wildlife on Wee WeeCay. The recent appearance of these pelicans is due to their old home on Pelican Island being destroyed by development. The population was made up of young pelicans that have white bellies and are smaller in size. Matured Brown Pelicans all have brown bellies, but females have a yellow color on their beaks (Ridgelyand Gwynne, 1989). We observed males, females, and young pelicans on Wee WeeCay. After observing the pelicans’aggressive dives, we formed two research questions: which side of the island do the pelicans prefer? and what time of day do the pelicans feed?

Photo credit: Callie Turlington

Methods: To conduct our experiment we used a 10 meter measuring device and a stopwatch. To determine the pelicans’ preferred side on the island we measured the concentration and intensity of bird droppings found on the mangrove leaves. We counted the number of bird dropping clusters every 10 meters from each side of the dock. We started from the right side of the main dock and measured to the wind-ward dock. Then we measured from the left side of the main dock and measure to the wind-ward dock. This gave us measurements for about 690 meters which covered the perimeter of Wee Wee Cay. We also rated the intensity of each cluster by observation on a scale from 1 to 10. The side with the higher concentration and intensity of bird droppings would be the preferred side of the island for the pelicans.

Photo credit: Myra Halpin

To determine the pelicans preferred feeding times we measured their rates of diving for food throughout different times during the day. We counted the number of dives for the group of about 15 pelicansin 10 minute intervals for 30 minutes. We made measurements at 6:307:00AM, 10:00-10:30AM, 1:50-2:20PM, 3:00-3:30PM, 5:00-5:30PM, and 5:30-6:00PM. By counting the number of dives in those time intervals, we could calculate the rate of diving for each 30 minutes interval to determine the pelicans’ preferred feeding times on Wee Wee Cay. Data:

Figure 1 shows the frequency of each intensity rating of the entire perimeter of Wee Wee Caye. The blue bar represents the measurements taken from the right side of the dock and the green bar represents the measurements taken from the left side of the main dock. This figure shows the difference of the intensities of bird droppings in the left and right side of the dock.

Figure 2 shows the number of bird dropping clusters for every ten meter increment. The blue line representthe measurements taken from the right side of the main dock and the green line represents measurements taken from the left side of the main dock. This graph shows the concentration of bird droppings around the perimeter of the island.

Figure 3 shows the total number of dives of the pelicans in ten minute intervals on Wee Wee Caye. This graph demonstrates the preferred feeding times of the pelicans.

Figure 4 shows the diving rates in dives per minutefor the pelicans in 30 minutes intervals. This graph also demonstrates the pelicans’ preferred feeding times.

Figure 5 shows the number of dives of a windy day. This graph shows that the diving rates of the pelicans are not changed by the weather conditions.

Discussion: After circling the island and counting the dropping clusters, we found that the majority of the pelican droppings are on the leeward side of the island. As you can see from Figure 2, there are not many clusters in the first few 10 meter increments from the dock on the leeward side. At about 40 meters on the left side and 50 meters on the right side, the number of clusters began to increase, but by the time we reached the dock on the windward side there were practically no clusters. The concentration of clusters was the highest on the leeward side of the island on the tips. This side of the island is a more desirable place to live because it is more protected from the weather. The intensity of the clusters was also highest at these points as you can see in Figure 1 showing that these are the places where the pelicans live and spend most of their time. In Figure 5 you can see that although the pelicans feed on and off throughout the day, there are three times when they eat a significant amount. Their morning feeding seemed to be between 10:00 and 10:30AM when they dove between 30 and 40 times in ten minutes. The

midday meal was between 3:00 and 3:30PM when they dove about 50 to 60 times in ten minutes. The most active time for the pelicans was always between 5:00 and 6:00PM when they dove about 100 times in ten minutes. This is obviously due to the fact that this is the time when their food sources, minnows, aremost easily accessible. The minnows have phototrophic behavior, so during the day they stay close to the island in the roots of the mangroves. This protects them from predators during the day, but they retreat to the deep water at night. During this transition, it is very easy for the pelicans catch the minnows (Paul, 2009). We also counted the pelican dives at different times during a windy day. As you can see from Figure 4, the rate of dives is not affected by the wind. Though it may not be as easy for them to fly, they still must eat.

Conclusion: Our researched showed that the brown pelican that inhabits Wee WeeCay prefers to live and feed on the lee-ward side of the island. They also prefer to eat at 5:00PM-6:00PM which is when the minnows migrate out making feeding easier for the pelicans.

Works cited

Ellison, Aaron M. and Elizabeth J. Farnsworth. 1996. Scale-Dependent Spatial and Temporal Variability in Biogeography of Mangrove Root EpibiontCommunities. 66:45-66. Ridgely, Robert S. and John A. Gwynne. 1989. A Guide to the Birds of the Panama. Princeton University Press. Princeton, New Jersey. Shave, Paul 2009. Personal Communication