Reproductive Success of the Common Tern (Sterna Hirundo) and Black Skimmer (Rynchops Niger) in Different Habitats in Virginia
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W&M ScholarWorks Dissertations, Theses, and Masters Projects Theses, Dissertations, & Master Projects 1982 Reproductive success of the common tern (Sterna hirundo) and black skimmer (Rynchops niger) in different habitats in Virginia Daniel Carey Smith College of William & Mary - Arts & Sciences Follow this and additional works at: https://scholarworks.wm.edu/etd Part of the Ecology and Evolutionary Biology Commons, and the Zoology Commons Recommended Citation Smith, Daniel Carey, "Reproductive success of the common tern (Sterna hirundo) and black skimmer (Rynchops niger) in different habitats in Virginia" (1982). Dissertations, Theses, and Masters Projects. Paper 1539625169. https://dx.doi.org/doi:10.21220/s2-6ptf-ps17 This Thesis is brought to you for free and open access by the Theses, Dissertations, & Master Projects at W&M ScholarWorks. It has been accepted for inclusion in Dissertations, Theses, and Masters Projects by an authorized administrator of W&M ScholarWorks. For more information, please contact [email protected]. REPRODUCTIVE SUCCESS OF THE COMMON TERN (STERNA HIRUNDO) AND BLACK SKIMMER (RYNCHOPS NIGER) IN DIFFERENT HABITATS IN VIRGINIA A Thesis Presented to The Faculty of the Department of Biology The College of William and Mary in Virginia In Partial Fulfillment Of the Requirements for the Degree of Master of Arts by Daniel Carey Smith 1982 APPROVAL SHEET This thesis is submitted in partial fulfillment of the requirements for the degree of Master of Arts Daniel Carey Smith, Author Approved, April 1982 Mitchell A. Byrd Ruth A. Beck Gregory M. Capelli Stewart A. Ware R. Michael Erwin, U.S. Fish and Wildlife Service TABLE OF CONTENTS Page ACKNOWLEDGMENTS........................ ii LIST OF TABLES. .......... iii LIST OF FIGURES ................ iv ABSTRACT.......... v INTRODUCTION......................................................... 2 LITERATURE REVIEW ................ 5 STUDY AREA AND METHODS.............. 17 RESULTS...................................... 26 DISCUSSION. ...................... 46 APPENDIX A .......................................... 53 LITERATURE CITED.................. 54 VITA. ................................................................. 60 ACKNOWLEDGMENTS I would like to express my utmost gratitude to Dr. Mitchell A. Byrd, who first interested me in seabird research, for providing much needed moral and logistical support throughout this study. I also thank Mrs. Ruth Beck, Dr. Gregory Capelli and Dr. Stewart Ware for their ctitical reading of the manuscript. Invaluable assistance with the data analysis was provided by David Reed of the William and Mary Computer Center and Ken Williams of the U.S. Fish and Wildlife Service. Bob Bower and Jewel Thomas of the William and Mary Biology Department also lent their technical expertise to the project. The Nature Conservancy allowed me to conduct research on the barrier islands of the Virginia Coast Reserve. The Eastern Shore Lab of the Virginia Institute of Marine Science provided storage facilities and technical assistance in 1980, and NASA's Wallops Island Flight Center, in cooperation with the Chincoteague National Wildlife Refuge, provided housing in 1981. I also owe many thanks to the members of my family and to Fenton Day for assisting with the field work. Finally, this thesis could not have been completed without the continual support and guidance of Dr. R. Michael Erwin of the U.S. Fish and Wildlife Service. He provided funding during both years of the study through the Non-game Section of the Patuxent Wildlife Research Center and advised me during every aspect of the project. I am forever indebted to him for his supervision, patience and friendship. ii LIST OF TABLES Table Page 1. Colony locations in Virginia-Maryland and New Jersey........... 21 2. Mean temperature and rainfall data............................ 29 •'i 3. Common tern nest and egg fate data............................ 33 4. Common tern clutch sizes and hatching success .............. 34 5. Common tern chick fate d a t a .................................. 35 6. Common tern fledging success.................................. 36 7. Black skimmer nest and egg fate data.......................... 37 v 8. Black skimmer clutch sizes and hatching success ............ 38 9. Black skimmer chick fate d a t a ................................ 39 10. Black skimmer fledging success................................ 40 11. Common tern conspecific nest spacing........... 41 12. Common tern heterospecific nest spacing .................... 42 13. Black skimmer conspecific nest spacing........................ 44 14. Black skimmer heterospecific nest spacing ................. 45 iii LIST OF FIGURES Figure Page 1. Colony locations on Eastern Shore of Virginia-Maryland . 22 2. Horsehead Tump and Cedar Island salt marsh island colonies . 23 3. Metomkin Island barrier island beach colonies............ 24 4. Smith Island barrier island beach colony .................. 25 5. Common tern and black skimmer initial egg-laying dates . 27 iv ABSTRACT The reproductive success of the common tern (Sterna hirundo) and black skimmer (Rynchops niger) was compared between barrier island beach and salt marsh island habitats. Parameters monitored to determine relative productivity included egg-laying dates, clutch size, hatching success, fledging success and nearest neighbor distance. Both species began egg-laying later in 1981 than in 1980, with no differences found between habitats. Common terns had significantly greater clutch sizes and hatching success rates on beach habitat than in the marsh and in 1980 than in 1981. Common tern fledging success showed no difference between habitats but was significantly greater for both habitats in 1980 than in 1981. Large scale colony washout and losses to predation in 1981 limited the sample size and may have negated any differences which existed by habitat. Black skimmer productivity data were not tested due to small sample sizes from the marsh habitat, but showed a reversal in trend from 1980 to 1981. Beach colonies of skimmers had greater success in all parameters in 1980, but were not as great as the marsh success rates in 1981. Common tern conspecific nest spacing was greater.on the beach than in the marsh and greater in 1981 than in 1980. Black skimmer conspecific nest spacing was greater on the beach also, but did not differ by year. Heterospecific nest spacing for both species was greater than the corresponding conspecific distance on the beach, was greater in distance on the beach and was greater in 1981 than in 1980. v REPRODUCTIVE SUCCESS OF THE COMMON TERN (STERNA HIRUNDO) AND BLACK SKIMMER (RYNCHOPS NIGER) IN DIFFERENT HABITATS IN VIRGINIA INTRODUCTION Common terns (Sterna hirundo) and black skimmers (Rynchops niger) have traditionally nested on barrier island beaches on the mid-Atlantic coast of the U.S. (Bailey 1913, Bent 1921, Austin 1929, Stone 1937, Palmer 1941, Erwin and Korschgen 1979). Recently, however, human encroachment has caused habitat shifts by terns and skimmers into alternative habitat types in some areas (Buckley and Buckley 1975, 1977, Burger 1977, Burger and Lesser 1977, Erwin 1980). Habitats now being used for breeding include salt marsh islands, dredge deposition sites, and man-made structures (Erwin 1979b). Recent coastal surveys (Erwin 1979b, Erwin and Korschgen 1979, Parnell and Soots 1980, Buckley and Buckley in press) have shown that the use of these alternative habitat types by traditional beach-nesters is greatest in states with the greatest degree of coastal zone development. An example of differential habitat utilization between areas of similar coastal structure can be seen in Virginia and New Jersey. In Virginia, where 85 per cent of the coastline is protected by private and Federal agencies, over 80 per cent of the beach-nesting seabirds are found on the barrier islands. In contrast, New Jersey has only 25 per cent of its coastline protected from unrestricted recreation, and only 10 per cent of the same species are found on the barrier islands, the remainder having moved into salt marsh areas. These dramatic shifts in breeding habitat use mean that each species must adapt to changes in the physical makeup of the habitat at 2 3 the colony and nest site as well as to changes in the biotic environment. The major factor affecting the relative fitness of the individual in different habitats include the risk of flooding of eggs and young (Greenhalgh 1974, Montevecchi 1978, Burger 1979a, Burger and Lesser 1979), the physical stability of the sand, rock and marsh substrates (McNicholl 1975, Southern 1977), predation (Buckley and Buckley 1972, Burger 1979, Burger and Lesser 1978) and competition for nest sites (Crowell and Crowell 1946, Nisbet 1973, Erwin 1980). These measures of habitat quality must be weighed against the effects of density of breeding birds within a particular habitat. Fretwell (1968) described habitat suitability as a density-dependent gradient.which varies from high quality with high density to low quality with lower density. Potential breeding birds might not settle in the habitat of highest quality if the density of the birds already utilizing that habitat would cause their success to be less than the average success of the local population. They might instead choose to colonize habitats of lower suitability because of the lower density. For ground-nesting seabirds such as the common tern and black skimmer, the shift from open, dry sandy beaches to more vegetated wet marshes of lower elevation represents a