Lipson report

Waterfowl Population Trends in Boston Harbor
Brian Lipson
Lexington High School, March 2005

Abstract

It might seem that the recent measures to clean up Boston Harbor would be beneficial for waterfowl, but this may not be the case. Even though cleaner water is better for human activities, it may have fewer nutrients for life in Boston Harbor.
To examine the effects of the harbor cleanup on waterfowl, I studied the population trends of six important bird species seen in Boston Harbor. I used information from my own participation and historical data from two different annual bird surveys. One is "Take A Second Look" (TASL), an organization that has been counting waterfowl in Boston Harbor for the last 25 years, and the other is the Audubon-sponsored Christmas Bird Count (CBC). I participated in each of the three winter 2004-2005 TASL bird counts and in one regional CBC.

The birds I studied were Brant Branta bernicla, Common Eider Somateria mollissima, Red-breasted Merganser Mergus serrator, American Black Duck Anas rubripes, Common Goldeneye Bucephala clangula, and Bufflehead Bucephala albeola. Using TASL data, these species were found to decline on average by about 5% to 22% per year since 1998. These results are in good agreement with Greater Boston CBC data for a similar period. CBC data from Plymouth, Massachusetts, a location unaffected by harbor cleanup, was used as a control. Populations in Plymouth have been relatively stable or slowly increasing. This supports the hypothesis that waterfowl have been declining in Boston Harbor because the cleanup has resulted in lower nutrient levels in the water.

Introduction

Although recent measures to clean up Boston Harbor would seem to be beneficial for waterfowl, this may not be true. Even though cleaner water is better for human activities, it may have fewer nutrients for life in Boston Harbor. Therefore, the purpose of this project is to assess the impact of the harbor cleanup on waterfowl and determine the influence of lower nutrient levels and cleaner water on the birds. In order to monitor the populations of birds in Boston Harbor, the "Take A Second Look" (TASL) organization has been conducting bird censuses in Boston Harbor for twenty-five years. I participated in all three winter TASL counts for 2004-2005, helping count birds on a route around the harbor, including South Boston and East Boston. I went with Soheil Zendeh, a co-founder of TASL, and together we recorded the number of birds for our section of the TASL count.

In addition to using the data I took with TASL, I also used historical data from TASL and the Audubon-sponsored Christmas Bird Count (CBC). The CBC has been going on for about one hundred years and annually counts birds all over the continent. Although the CBC doesn't focus on Boston Harbor, I was able to use data from the CBC from Greater Boston as an independent check on the TASL data. CBC data from Plymouth, Massachusetts, a location unaffected by harbor cleanup, was used as a control. I also participated in a regional CBC along with expert birder Ron Lockwood to become familiar with CBC data collecting methods.

After Soheil Zendeh helped me come up with the idea that the most common birds in Boston Harbor might be declining in the last few years, I looked at TASL data for Brant, Common Eider, Red-breasted Merganser, American Black Duck, Common Goldeneye, and Bufflehead.

Procedure

Materials. While on bird counts, I used a pair of Bushnell Explorer 10x25 binoculars and a Kodak EasyShare DX6490 digital camera. On TASL counts, I also used a Kowa TSN-2, 20-60x zoom spotting scope. In addition to the data I helped take, I got data from the TASL and CBC online databases (see bibliography).

Procedure.There are two main parts to the procedure. The first consisted of observing birds while participating in bird surveys. The other was choosing the appropriate historical data to use from TASL and CBC and analyzing the data to determine population trends.

On November 21, 2004, January 9, 2005, and February 6, 2005, I took part in Boston Harbor bird censuses conducted by TASL. There are eleven different parties that count birds in seven different areas of the harbor. The Boston Harbor data I used for birds from TASL includes birds counted in Nahant, Boston, Winthrop, Squantum, Weymouth, Hough's Neck, and Hull. I went with Soheil Zendeh, and the two of us counted birds on a route through South Boston and East Boston (the same route has been in use for years so that there is consistency from year to year). Starting early in the morning, we counted birds until early afternoon. We looked in lakes and rivers that connected to Boston Harbor and sections of the harbor itself. Usually, when we arrived at a place to count birds, we got out spotting scopes and scanned all the visible birds near water and counted them.
In addition, on January 2, 2005, I was led by Ron Lockwood, and helped count birds for CBC in the Assabet River National Wildlife Refuge. Although I personally never used the data we took that day, it will go into the CBC database, and it helped me to become familiar with CBC data collecting methods. We counted birds from early morning to early afternoon, walking on trails within the reserve. We spotted birds with the naked eye and with binoculars mostly in trees, but also in marshy wetlands.

In order to get the most relevant and useful data for waterfowl population trends, several decisions had to be made to determine which ducks seen by TASL to use for analysis. I decided to use the most common waterfowl seen by TASL because bigger samples of data will have more reliable trends than data for species that are not seen regularly. However, I could not use the total of all birds seen by TASL each year because there are some species of birds counted whose populations don't necessarily reflect environmental factors.
"Park birds" such as Canada Geese and Mallard adapt to humans, getting food easily from humans and living in human-made environments. Therefore, I omitted Canada Geese and Mallard from the top ten birds seen in the harbor.
Scoter, which seemed to be one of the more common birds seen in the harbor, had somewhat inconsistent data.
Scaup was another common species seen in the harbor, but when CBC data was checked for Scaup, there was very inconsistent, unreliable data for both Greater Boston and Plymouth (such as there not being any seen for a few years and then seeing hundreds the next year).
The six remaining species from the ten most common were used in this project: Brant, Common Eider, Red-breasted Merganser, American Black Duck, Common Goldeneye, and Bufflehead. For these six species, I looked at Greater Boston CBC data in order to verify the TASL data from the harbor. CBC populations from Plymouth (a place unaffected by the harbor cleanup) were used as a control. Each of the six species had reliable data from both sources. The six bird species used represent the overall trend for waterfowl populations in the harbor because they are the most commonly seen birds. Overall, there are 31 bird species seen in Boston Harbor (by TASL). The total number of birds seen each year, averaged over the period 1998-2003 is 18,533. The sum of the average populations for the six species used is 14,283. Thus, the six species used comprise 77.1 % of the total birds seen.

I used January TASL data because they are in the closest proximity to CBC data. This allows the use of CBC data to check the TASL data. I looked at population trends for a period of years that differs between TASL (1998 to 2005) and CBC (1992-1993 to 2003-2004) because I tried to obtain the clearest trends possible. The data sets for Boston from TASL and CBC were compared and found to be consistent.

Results

For each of the six bird species used, Common Eider, Brant, Red-breasted Merganser, American Black Duck, Common Goldeneye, and Bufflehead, data were collected and three graphs were made: TASL (Boston Harbor), Greater Boston CBC, and Plymouth CBC. These three data sources were also used to make graphs for the combined populations of the six species. For each of the three graphs for each of the six birds, and for each of the three graphs of total population, I made exponential regressions to model the data.

Exponential models were used instead of linear ones because linear models would keep declining, eventually reach zero, and become negative (which clearly is not appropriate for a bird population). Exponential models are also useful because they show the percent decline each year based on the size of the new population for that year. The equations for each of the exponential regressions were found (see graphs). Each equation is in the form 'Population' = Ce^kt, where 'C' is a constant, 'k' is the exponential rate, and 't' is time (in years). Based on that equation, the next year's equation is 'Population' = Ce^k(t+1). The ratio between the second year's population and the first year's is thus (Ce^k(t+1))/(Ce^kt). That ratio simplifies to e^k. So, the expression I used to find the average percent decline for each exponential regression was e^k-1 (the minus one for putting the final result in terms of a decimal between 0 and 1).

The results for population trends are shown in the accompanying tables and bar charts. Bird populations derived from TASL data all declined in Boston Harbor by at least an average of five percent per year in the last eight years (with Brant declining by about 22%). The combined TASL populations for all six species declined on average by 9.1% per year. Populations from the Greater Boston CBC data declined on average by amounts ranging from .9 to 7.7% per year over a period of 12 years. The combined Greater Boston CBC populations declined on average by 6.7% per year. These results are in very good agreement. The difference between the combined percent declines gives an idea of the amount of uncertainty in the bird population trends.

I used Plymouth CBC data as a control. Bird populations derived from Plymouth CBC data range from declining on average by 4.6% to increasing on average by 8.8% per year over a period of 12 years. The combined Plymouth CBC populations increase on average by 2.1% per year.

These results are consistent with my hypothesis that waterfowl populations in Boston Harbor have declined during the period of harbor cleanup. In addition, populations did not appear to decline in Plymouth, where birds may not have been affected by harbor cleanup.

Discussion and conclusions
The declining trends of Common Eider, Brant, Red-breasted Merganser, American Black Duck, Common Goldeneye, and Bufflehead may be connected to recent harbor cleanup efforts and the effects the cleanup has had on the harbor environment. In cleaning up the harbor, the amount of sewage dumped into the water was reduced, and there has been a resulting reduction in the nutrient levels in the harbor (as described on the MWRA web page).

The accompanying bar graph (from MWRA web page) shows the decline in solids discharged into the water during the period of the harbor cleanup. The graph of chlorophyll concentrations in the harbor (from Taylor, 2004) shows a dramatic decrease over the same period. The graph shows the levels of chlorophyll as a function of distance from land, both before and after major efforts to clean up the harbor. The greatest change is within the harbor, where the chlorophyll levels fell by a factor of two.

Declining chlorophyll levels are an indication of declining plant matter entering the food chain. This is presumed to be due to the reduced levels of nutrients in the water. Since waterfowl are near the top of the food chain in the harbor, a reduction of nutrients can potentially have a profound effect on the birds.

In the future, I would find data for other locations around Massachusetts to see if they have bird population trends more similar to Boston Harbor or to Plymouth. If some have trends like that in Boston Harbor, are those locations facing similar cleanup efforts? Is the small increase in waterfowl populations in the last several years in Plymouth an exception? If the trends in other locations are more like the ones in Plymouth, that would strengthen my hypothesis that cleanup efforts in Boston Harbor are the cause for the decline in bird populations.

In addition, I would try to compare November and February TASL data to the January data to obtain a more complete picture of the population trends in Boston Harbor.

The effects of the Boston Harbor cleanup on the environment are very complex (see Worms, fish, birds, mammals and the Harbor clean-up). Also, there are many factors that can influence bird populations. The data from Boston Harbor and Plymouth examined in this project suggest there may be a connection between the cleanup and the declining populations of certain birds in Boston Harbor.

Acknowledgements

I would like to thank Soheil Zendeh, a co-founder of TASL, very much. He allowed me to take part in TASL counts and taught me numerous ways to improve counting and identifying birds. In addition, he helped me think of ideas for my project and explained many scientific concepts.

I would like to thank Maury Hall, the TASL data compiler, for providing me with several detailed explanations about the decline of birds in the harbor.

I would like to thank Ron Lockwood for allowing me to do the Christmas Bird Count and giving me several ideas for my project.

I would also like to thank H. Heusmann for answering my questions and giving me information for my project.

Finally, I would like to thank my father, Steven Lipson, for encouraging me throughout my project, editing my work, and helping me with ideas.

Bibliography

Christmas Bird Count Homepage. Audubon Society.
MWRA Online. Massachusetts Water Resources Authority.
Sibley, David. National Audubon Society The Sibley Guide to Birds. New York. Alfred A. Knopf. 2000.
Sibley, David. Sibley Guide to Bird Life and Behavior. New York. Alfred A. Knopf. 2001.
Taylor D. 2004. Harbor - Bay eutrophication-related water chemistry changes after 'offshore transfer'. Boston: Massachusetts Water Resources Authority. Report ENQUAD 2004-06.
Zendeh, Soheil. TASL Online..

last updated: 21 September 2005
url: http://www.gis.net/~szendeh/tbrian.lipson.report.htm

	Waterfowl Population Trends in Boston Harbor Brian Lipson Lexington High School, March 2005 Abstract It might seem that the recent measures to clean up Boston Harbor would be beneficial for waterfowl, but this may not be the case. Even though cleaner water is better for human activities, it may have fewer nutrients for life in Boston Harbor. To examine the effects of the harbor cleanup on waterfowl, I studied the population trends of six important bird species seen in Boston Harbor. I used information from my own participation and historical data from two different annual bird surveys. One is "Take A Second Look" (TASL), an organization that has been counting waterfowl in Boston Harbor for the last 25 years, and the other is the Audubon-sponsored Christmas Bird Count (CBC). I participated in each of the three winter 2004-2005 TASL bird counts and in one regional CBC. The birds I studied were Brant Branta bernicla, Common Eider Somateria mollissima, Red-breasted Merganser Mergus serrator, American Black Duck Anas rubripes, Common Goldeneye Bucephala clangula, and Bufflehead Bucephala albeola. Using TASL data, these species were found to decline on average by about 5% to 22% per year since 1998. These results are in good agreement with Greater Boston CBC data for a similar period. CBC data from Plymouth, Massachusetts, a location unaffected by harbor cleanup, was used as a control. Populations in Plymouth have been relatively stable or slowly increasing. This supports the hypothesis that waterfowl have been declining in Boston Harbor because the cleanup has resulted in lower nutrient levels in the water.
	Introduction Although recent measures to clean up Boston Harbor would seem to be beneficial for waterfowl, this may not be true. Even though cleaner water is better for human activities, it may have fewer nutrients for life in Boston Harbor. Therefore, the purpose of this project is to assess the impact of the harbor cleanup on waterfowl and determine the influence of lower nutrient levels and cleaner water on the birds. In order to monitor the populations of birds in Boston Harbor, the "Take A Second Look" (TASL) organization has been conducting bird censuses in Boston Harbor for twenty-five years. I participated in all three winter TASL counts for 2004-2005, helping count birds on a route around the harbor, including South Boston and East Boston. I went with Soheil Zendeh, a co-founder of TASL, and together we recorded the number of birds for our section of the TASL count. In addition to using the data I took with TASL, I also used historical data from TASL and the Audubon-sponsored Christmas Bird Count (CBC). The CBC has been going on for about one hundred years and annually counts birds all over the continent. Although the CBC doesn't focus on Boston Harbor, I was able to use data from the CBC from Greater Boston as an independent check on the TASL data. CBC data from Plymouth, Massachusetts, a location unaffected by harbor cleanup, was used as a control. I also participated in a regional CBC along with expert birder Ron Lockwood to become familiar with CBC data collecting methods. After Soheil Zendeh helped me come up with the idea that the most common birds in Boston Harbor might be declining in the last few years, I looked at TASL data for Brant, Common Eider, Red-breasted Merganser, American Black Duck, Common Goldeneye, and Bufflehead.
	Procedure Materials. While on bird counts, I used a pair of Bushnell Explorer 10x25 binoculars and a Kodak EasyShare DX6490 digital camera. On TASL counts, I also used a Kowa TSN-2, 20-60x zoom spotting scope. In addition to the data I helped take, I got data from the TASL and CBC online databases (see bibliography). Procedure.There are two main parts to the procedure. The first consisted of observing birds while participating in bird surveys. The other was choosing the appropriate historical data to use from TASL and CBC and analyzing the data to determine population trends. On November 21, 2004, January 9, 2005, and February 6, 2005, I took part in Boston Harbor bird censuses conducted by TASL. There are eleven different parties that count birds in seven different areas of the harbor. The Boston Harbor data I used for birds from TASL includes birds counted in Nahant, Boston, Winthrop, Squantum, Weymouth, Hough's Neck, and Hull. I went with Soheil Zendeh, and the two of us counted birds on a route through South Boston and East Boston (the same route has been in use for years so that there is consistency from year to year). Starting early in the morning, we counted birds until early afternoon. We looked in lakes and rivers that connected to Boston Harbor and sections of the harbor itself. Usually, when we arrived at a place to count birds, we got out spotting scopes and scanned all the visible birds near water and counted them. In addition, on January 2, 2005, I was led by Ron Lockwood, and helped count birds for CBC in the Assabet River National Wildlife Refuge. Although I personally never used the data we took that day, it will go into the CBC database, and it helped me to become familiar with CBC data collecting methods. We counted birds from early morning to early afternoon, walking on trails within the reserve. We spotted birds with the naked eye and with binoculars mostly in trees, but also in marshy wetlands.
	In order to get the most relevant and useful data for waterfowl population trends, several decisions had to be made to determine which ducks seen by TASL to use for analysis. I decided to use the most common waterfowl seen by TASL because bigger samples of data will have more reliable trends than data for species that are not seen regularly. However, I could not use the total of all birds seen by TASL each year because there are some species of birds counted whose populations don't necessarily reflect environmental factors. "Park birds" such as Canada Geese and Mallard adapt to humans, getting food easily from humans and living in human-made environments. Therefore, I omitted Canada Geese and Mallard from the top ten birds seen in the harbor. Scoter, which seemed to be one of the more common birds seen in the harbor, had somewhat inconsistent data. Scaup was another common species seen in the harbor, but when CBC data was checked for Scaup, there was very inconsistent, unreliable data for both Greater Boston and Plymouth (such as there not being any seen for a few years and then seeing hundreds the next year). The six remaining species from the ten most common were used in this project: Brant, Common Eider, Red-breasted Merganser, American Black Duck, Common Goldeneye, and Bufflehead. For these six species, I looked at Greater Boston CBC data in order to verify the TASL data from the harbor. CBC populations from Plymouth (a place unaffected by the harbor cleanup) were used as a control. Each of the six species had reliable data from both sources. The six bird species used represent the overall trend for waterfowl populations in the harbor because they are the most commonly seen birds. Overall, there are 31 bird species seen in Boston Harbor (by TASL). The total number of birds seen each year, averaged over the period 1998-2003 is 18,533. The sum of the average populations for the six species used is 14,283. Thus, the six species used comprise 77.1 % of the total birds seen. I used January TASL data because they are in the closest proximity to CBC data. This allows the use of CBC data to check the TASL data. I looked at population trends for a period of years that differs between TASL (1998 to 2005) and CBC (1992-1993 to 2003-2004) because I tried to obtain the clearest trends possible. The data sets for Boston from TASL and CBC were compared and found to be consistent.
	Results For each of the six bird species used, Common Eider, Brant, Red-breasted Merganser, American Black Duck, Common Goldeneye, and Bufflehead, data were collected and three graphs were made: TASL (Boston Harbor), Greater Boston CBC, and Plymouth CBC. These three data sources were also used to make graphs for the combined populations of the six species. For each of the three graphs for each of the six birds, and for each of the three graphs of total population, I made exponential regressions to model the data.
	Exponential models were used instead of linear ones because linear models would keep declining, eventually reach zero, and become negative (which clearly is not appropriate for a bird population). Exponential models are also useful because they show the percent decline each year based on the size of the new population for that year. The equations for each of the exponential regressions were found (see graphs). Each equation is in the form 'Population' = Ce^kt, where 'C' is a constant, 'k' is the exponential rate, and 't' is time (in years). Based on that equation, the next year's equation is 'Population' = Ce^k(t+1). The ratio between the second year's population and the first year's is thus (Ce^k(t+1))/(Ce^kt). That ratio simplifies to e^k. So, the expression I used to find the average percent decline for each exponential regression was e^k-1 (the minus one for putting the final result in terms of a decimal between 0 and 1). The results for population trends are shown in the accompanying tables and bar charts. Bird populations derived from TASL data all declined in Boston Harbor by at least an average of five percent per year in the last eight years (with Brant declining by about 22%). The combined TASL populations for all six species declined on average by 9.1% per year. Populations from the Greater Boston CBC data declined on average by amounts ranging from .9 to 7.7% per year over a period of 12 years. The combined Greater Boston CBC populations declined on average by 6.7% per year. These results are in very good agreement. The difference between the combined percent declines gives an idea of the amount of uncertainty in the bird population trends. I used Plymouth CBC data as a control. Bird populations derived from Plymouth CBC data range from declining on average by 4.6% to increasing on average by 8.8% per year over a period of 12 years. The combined Plymouth CBC populations increase on average by 2.1% per year. These results are consistent with my hypothesis that waterfowl populations in Boston Harbor have declined during the period of harbor cleanup. In addition, populations did not appear to decline in Plymouth, where birds may not have been affected by harbor cleanup.
	Discussion and conclusions The declining trends of Common Eider, Brant, Red-breasted Merganser, American Black Duck, Common Goldeneye, and Bufflehead may be connected to recent harbor cleanup efforts and the effects the cleanup has had on the harbor environment. In cleaning up the harbor, the amount of sewage dumped into the water was reduced, and there has been a resulting reduction in the nutrient levels in the harbor (as described on the MWRA web page).
	The accompanying bar graph (from MWRA web page) shows the decline in solids discharged into the water during the period of the harbor cleanup. The graph of chlorophyll concentrations in the harbor (from Taylor, 2004) shows a dramatic decrease over the same period. The graph shows the levels of chlorophyll as a function of distance from land, both before and after major efforts to clean up the harbor. The greatest change is within the harbor, where the chlorophyll levels fell by a factor of two. Declining chlorophyll levels are an indication of declining plant matter entering the food chain. This is presumed to be due to the reduced levels of nutrients in the water. Since waterfowl are near the top of the food chain in the harbor, a reduction of nutrients can potentially have a profound effect on the birds. In the future, I would find data for other locations around Massachusetts to see if they have bird population trends more similar to Boston Harbor or to Plymouth. If some have trends like that in Boston Harbor, are those locations facing similar cleanup efforts? Is the small increase in waterfowl populations in the last several years in Plymouth an exception? If the trends in other locations are more like the ones in Plymouth, that would strengthen my hypothesis that cleanup efforts in Boston Harbor are the cause for the decline in bird populations. In addition, I would try to compare November and February TASL data to the January data to obtain a more complete picture of the population trends in Boston Harbor. The effects of the Boston Harbor cleanup on the environment are very complex (see Worms, fish, birds, mammals and the Harbor clean-up). Also, there are many factors that can influence bird populations. The data from Boston Harbor and Plymouth examined in this project suggest there may be a connection between the cleanup and the declining populations of certain birds in Boston Harbor. Acknowledgements I would like to thank Soheil Zendeh, a co-founder of TASL, very much. He allowed me to take part in TASL counts and taught me numerous ways to improve counting and identifying birds. In addition, he helped me think of ideas for my project and explained many scientific concepts. I would like to thank Maury Hall, the TASL data compiler, for providing me with several detailed explanations about the decline of birds in the harbor. I would like to thank Ron Lockwood for allowing me to do the Christmas Bird Count and giving me several ideas for my project. I would also like to thank H. Heusmann for answering my questions and giving me information for my project. Finally, I would like to thank my father, Steven Lipson, for encouraging me throughout my project, editing my work, and helping me with ideas. Bibliography Christmas Bird Count Homepage. Audubon Society. MWRA Online. Massachusetts Water Resources Authority. Sibley, David. National Audubon Society The Sibley Guide to Birds. New York. Alfred A. Knopf. 2000. Sibley, David. Sibley Guide to Bird Life and Behavior. New York. Alfred A. Knopf. 2001. Taylor D. 2004. Harbor - Bay eutrophication-related water chemistry changes after 'offshore transfer'. Boston: Massachusetts Water Resources Authority. Report ENQUAD 2004-06. Zendeh, Soheil. TASL Online..

Waterfowl Population Trends in Boston Harbor Brian Lipson Lexington High School, March 2005

Abstract

Introduction

Procedure

Results

Discussion and conclusions

Acknowledgements

Bibliography

Waterfowl Population Trends in Boston Harbor
Brian Lipson
Lexington High School, March 2005