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Sanderling Feeding Patterns
By: Paul Skapik, Melissa Moriarty, Sarah Sturgill, & Kristy Krumnacher TPTE 595 Dr. Melear Ossabaw Island Experiment May 25-29, 2002
Abstract
The purpose of our study was to learn more about the feeding patterns of Sanderlings, Calidris alba. We were interested in seeing if any feeding differences occurred due to the different tides. In order to do this, we recorded the number of pecks per minute at various times of the day, noting the different tides. We also studied any differences in the amount of birds in a group, as compared to the pecks per minute.
Hypothesis
Do Sanderlings feed more at high tide or low tide? Does the size of the group affect the Sanderlings’ pecking?
Introduction
The Calidris alba, more commonly called the Sanderling is a species of Sandpiper and belongs to the family of Scholopacidae. The birds usually dwell along the shore or beach and are usually 18-21 centimeters long. They breed in the colder portions of the northern hemisphere and migrate south where they make their home during the winter months. The bird stays mainly on the coast along sandy beaches, mudflats, and coastal pools and is rarely seen inland. It is a silent bird and usually stays in flocks.
The Sanderling is interesting to watch as it gracefully chases the receding water. The waves leave an abundance of its particular food as they move in and out. The birds usually feast on sea worms, small bivalve shells, and crustaceans, though it will also eat buds and insects. As you watch the eager birds along the shoreline scurrying around for food it seems as though they are never satisfied. When in search of food they are always busy and moving in the wake as the waves retreat. Unlike the other members of its family, the feet of the Sanderling have neither a forth toe nor membrane and are totally divided. This helps the Sanderling to quickly run and walk on firm surfaces.
Conducting the experiment on the Sanderling was not difficult considering the birds are unwary of humans and natural disturbances. Sometimes a flock will rise up together as though they were being summoned. After a few simultaneous turns they will recommence the area from which they had left. It was delightful to sit on the beach and observe the graceful movements of the birds.
Materials & Methods
In order to study the feeding patterns of Sanderlings, our group decided to count the number of pecks per minute of individual Sanderlings. We took a sample of three birds, on average, from each group to watch for one minute. In order to not scare off the birds, we watched from a distance with binoculars. One person counted the pecks for one minute while another person timed the minute on a stopwatch. The results were recorded in the field notebook. Later, averages from the groups were taken.
Step One. Observation / Data Gathering
Because of the limited time afforded this experiment, our group could only obtain data from one day which totaled eleven different bird groupings. Time limitations also negated any follow-up observations to verify original data.
Sanderling's Observation (Data Results)
Bird Group 1: 33 birds (tight cluster)
11:30 AM- high tide
- 61 ppm (pecks per minute)
- 51 ppm
- 29 ppm
Bird Group 2: 80 birds (spread out)
11:45 AM- high tide, on sandbar
- 24 ppm
- 36 ppm
- 19 ppm
Bird Group 3: 35 birds (tight cluster)
12:00 PM- birds resting on beach
0 ppm (birds not eating- rested for 20 minutes)
Step Two. Decipher the Data. After collecting the basic data, we placed the raw data into two basic graphs to determine how best to proceed. These graphs were used to help formulate the findings in our extrapolations, as noted in the next step.
Chart One. Bird Groups Listed According to Time of Day and Size of Group.
Total Birds per Group (33) (80) (35) (25) (4) (9) (20) (35) (70) (16) (11) Time of Day 1130 1145 1200 1200 1200 1215 1215 1530 1540 1710 1730
Group 1
Group 2
Group
Group 4
Group 5
Group 6
Group 7
Group 8
Group 9
Group 10
Group 11
Chart two. Average Pecks Per Minute per Group. Note: Birds in Groups 3,4,& 7 were at rest, they were not feeding.
47
26
0 0
18
22
0
46
34
10
13
0
5
10
15
20
25
30
35
40
45
50
Group 1
Group 2
Group 3
Group 4
Group 5
Group 6
Group 7
Group 8
Group 9
Group 10
Group 11
Table 1 P-Value for Small Group and Middle Sized Group 0. P- Value for Small Group and Big Group 0. P-Value for Medium Sized Group and Large Group 0.
_ =.
Step Four. Summantion.
Discussion Our results show no significant difference (p-value = .13) between the tide level and the amount the birds peck. However, our data is limited due to the limited time we had to collect data. The results from Graph 1 do suggest a trend that at high tide the birds are pecking more. This trend could be due to several things. One is that the water at high tide was beginning to go back down. This could mean that species that the birds were eating were being washed up and left behind. There could possibly have been more food at that time because of high tide. This was also the earliest time of the day that we collected data. The birds could need more food in the morning than later on in the day. The need for food could come from the energy they will use during the day.
We also compared the amount of birds in a group to the average pecks per minute. While the data shows no significant difference (Table 1), there is a trend that the medium sized group (33 birds) pecks more per minute. This could be because the small group of four was feeding in a place where there was little food, and consequently that is why there were only four birds in that particular place and such low number of pecks. The group of 80 birds, the large group, could have been feeding in a location with a large quantity of food and therefore it was not necessary to peck faster because of the abundance. Since the data showed no significant difference between groups, the number of birds in a group simply may not influence the birds pecking. Future studies are needed.
The data collected is limited and there is a lack of replication for the collected data. Time was a constraint that caused the limited data collection. In the future more data should be collected to determine any significant trends in the feeding habits of shore birds. A future experiment should also include gathering a sample of what the birds are eating to compare the amount of food available to the pecks per minute. There was also a problem of being able to see the birds clearly. We did have to somewhat approach the birds, which could have possibly disturbed their natural eating habits. In the future a scope should be used to accurately count the number of pecks.
Conclusion
The data shows no significant difference between the different tides and the amount of pecking or between the number of birds in a group compared to the pecks per minute. There was a strong trend for more pecking at high tide, which could possibly mean
more available food at high tide. Future experiments will have to be conducted that include a longer time range for collection, replicated samples, and better equipment.
Bibliography
“Sanderling” Encyclopedia Britannica www.britannica.com/eb/article?eu= [accessed June 13, 2002]
“Birds and Nature: The Sanderling” www.birdnature.com/jun1901/sanderling [accessed June 13, 2002]
Alden, Peter. National Audubon Society: Field Guide To The Southeastern States. New York: Chanticleer Press, Inc., 1999
