- ~ . '· - U B.R. '· · USFW~ Anchorage
Population and Productivity Surveys of
Black-Legged Kittiwakes, Common Murres, and Pelagic Cormorants
at Cape Peirce, Alaska, Summer 1987
by Lisa Haggblom and Allyn O'Neil Togiak NWR ·Volunteers
Key Words: black-legged kittiwake, common murre, pelagic cormorant, Cape Peirce, seabird population, seabird productivity
U.S. Fish and Wildlife Service Togiak National Wildlife Refuge P.O. Box 270 Dillingham, Alaska 99576
I'
. Novembe r 30, 1987 ' j ... \ .
.,-· ., ( .. 1
INTRODUCTION There is a growing ·concern over the recent decline of many seabird species in the Bering Sea. Cape Peirce, within Togiak National Wildlife Refuge, reportedly has the largest seabird colony along the mainland coast of Alaska
Population Counts
The 1987 seabird study . began May 25, shortly after volunteers arrived at Cape Peirce, and ended September 9. Black legged kittiwakes, common murres, and pelagic cormorants were studied because they were most visible on the cliff ledges and the most ~bundant species. Black and white, 8 x 10 photographs taken i~ 1976 and 1984 outlined each study plot. Using· binoculars and/or a spotting scope, volunteers counted only those birds within the boundary lines as deline<;ited in the photographs. Aluminum stakes, set up by previous researchers in 1984, mark observation points , and insure consistent study plot identification between years. To make counting easier and hence ~ore accurate, individual ahd groups of birds were counted separately. For e>:~mple, a group of bir·ds was any number of birds isolated from others of its species by two or more body lengths, or by a bird of another species. Major study plots were census~d three to four times a week, and censusi ng was conducted at aP.pro:·: i matel y the same time of day to reduce diurnal variance. Population counts for 1987 are compared with data from previous years. As Higgins and Herter (1985) recommended, population counts from each study plot were averaged from May 25 to September 9, the~ the study plot averages totaled. The total area of all the study plots was determined to be approximately one-half the total occupied mainland ar~a, so the census averages Were multiplied by two to give the total mainland populations rJ ,' 2 Plot 27 was destroyed due to wave action and erosion between October 1986 and May 1987. Plot 41 was eliminated irom censusing due to observer disturbance to the seabirds. Shaiak Island is a small, rocky island adjacent to plots 1-18 on the southeast coast of the Cape Peirce peninsula, and attracts most of the seabird population that would otherwise nest on the mainland. Therefore, these plots were observed infrequently due to to 'their consistently low population numbers. Due to time limitations, Plot 29 was also observed infrequently. Censuses of the above mentioned plots could be conducted ever'y 2-3 years. Plot 20.4 was subdivided into three subplots to facilitate more accurate counting--20.41, 20.42, and 20.43. Productivity BLACK-LEGGED KITTIWAKES AND PELAGIC CORMORANTS Only study plots where the birds could be viewed easily with the naked eye or binoculars were included in the producti~ity surveys. The same photographs used for population counts were covered with plastic overlays. Each nest site ·Was then circled and numbered on the photos and observed every one to five days throughout the breeding season. Approximate dates of egg~laying, hatching, predation, and fledging were recorded. The number of successful kittiwake and cormorant nest attempts was calculated as the number of nests containing eggs per totai number of nests. Mean clutch size was cal~ulated only for those kittiwake and cormbrant nests with eggs. Hatching success was calculated as the number of chicks hatched per number of eggs laid. In addition, number of eggs hatched per total. number of nests was also .noted for kittiwakes COMMON MURRES Murres do not build nests, but lay their eggs directly on cliff ledges. The eggs and chicks are obscured from view by the adults. Consequently, murre chicks were not identified until they were ready to leave the cliff ledges, or until they were 1.' seen swimming in the water with the adults prior to flying tiffshore. The above parameters des~ribed for kittiwakes and cormorants were not applicable to murres as such, but the number of fledgl~ngs was compared with the total population of murres. "' ., ' . l. 3 RESULTS AND DISCUSSION Black-legged Kittiwakes The population of black-legged kittiwakes at Cape Peirce in 1987 <4,020) is approximately 1.7 times that of 1986 <2,440), and comparable to that of 1985 <3,800) is typically low, but was greater in 1987 than 1984-1986 C0-1%). Common Mur·r·es The population of common murres for 1987 <5,735) was comparable to that of 1986 <5,000), yet half the estimated population for 1985 (10,300) Pelagic Cormorants. The population of pelagic cormorants declined slightly from 1985 and 1986, yet it is not known whether this i~ a significant decrease 5 and began mid-JuMe continuing through the end of July. The first chicks were seen on study plot 31 on June 27, and appeared to be at least a few days old Low-flying pl~nes disturbed all species of nesting seabirds on several occasions in 1987. Adults left the nest ~ites and returned a short time later most often when planes flew along the cliff ledges at low elevations. Fishing boats traveling close to the shoreline also disturbed the seabirds in the same manner as aircraft, yet were fewer in number from mid-May to October. CONCLUSIONS Black-legged Kittiwakes - The kittiwake population in 1987 was almost twice that of 1986, and although the productivity was low, it was higher than that of 1986 (Table 1). This contrasts with the apparent decline in population and productivity from 1985 to 1986. Lloyd <1985) hypothesized that sea surface temperature, wind speed, and precipitation correlated with seabird produ~tivity. His results showed no correlation between breeding performance and water temperature, but surprisingly, increased breeding performance with higher winds. There was a negative effect of precipitation on b~eedin9 perfo~mance. The salinity and temperature of the water column become more well-mixed with increased surface wind. The food supplies available to the birds become more constant as the food web becomes more homogeneous, potentially contributing to i~creased breeding success 6 and murres, may serve as i nd i cator·s of fo~d supplies for kittiwakes. Kittiwakes often arrived at sites to forage where alcids were already foraging. Ravens and gulls were one cause of egg mortality. There were approximately 5-6 pairs of adult ravens observed in the vicinity of the most regularly censused study plots, from May through July. The total number increased to a minimum of 25 birds during August and September, as the raven chicks fledged. The number of gulls also increased during August and September as these chick~ fledged. If the productivity declines ·again to zero, however, the population the.or·etically will decline as the long-lived adults die. It is important to monitor the birds on a longterm basis, to determine the reason for and extent of the decline. Extra precaution should be taken so as not to disturb the nesting seabirds, as this might play a role in cr·eating additional stress on the adults, and may be a reason for the abandonment of some eggs and/or chicks. Common Murres The murre population appeared to stabilize from 1986 to 1987, 'after the decline ~rom 1985 to 1986 Pelagic Cormorants The cormorants, although lower in total population estimates than 1986, appeared to have a successful breeding season in 1987. Ravens preyed predominantly on the eggs~· and red foxes preyed on young chicks. At least one parent was usually present at the nest site, and the parents were never observed to leave their nest in response to predator attacks. · . Future productivity surveys might include cormorants nesting off the main productivity plots, since cormorants do not nest as colonially as kittiwakes and murres. Also, nest sites should be obse~ved as early as the beginning of May to include more of the 7 breeding season. The study plots censused in 1987 were those which could be observed with minimal disturbance to the seabirds. Researchers should approach the plots quietly, and conduct censuses a minimum of 4 times a week. Low-flying aircraft and boat traffic should be minimized along the shoreline to reduce additional disturbances. •, .... ··-·· __..- / ,;./ .... ~~ - . ,t· Nt .... ;· ~.,.,.,-. .. ·· --) ·--- :;5·-;-·:·:-:·-·· ...... /'"". - ...... __..,..... - ..- .. ,...... ___., Shaiak I Cape Peirce • Figure 1 Cape Peirce Peninsula, Bristol Bay, Alaska • ... 0 ) " .lo . . ' Figure 2. Cape Peirce seabird colonies, Bristol Bay. ------ .· 10 Table 1. Mainland population estimates for seabird species at Cape Peirce, Alaska, 1985-1987. ======~======SPECIES 1985 1986 1987 Black-legged kittiwake 3,800 2,449 4,020 Common murre 10,300 5,000 5,735 Pelagic cormo~ant 200 200 140 ======All 1986 data frbm Van Hulsteyn and Kavanaugh (1987); 1985 data from Higgins <1985>; 1984 data from Johnson and Baker (1985). ·. 11 Table 2. Census average of each study plot for black-legged kittiwakes, common murres, and pelagic cormorants at Cape Peir·ce, May 25 to September 9, 1987. ======PLOT SPECIES DAYS SAMPLED ELKI COMU PECO HOF'U TUPU ------~---~------43 62 59 0.6 1. 4 0.2 48 42 45 159 0.2 0.3 0.2 48 41 11 0 0.0 0.0 o.o 1 40 26 68 0.6 2.8 2.2 49 39 18 11 0.7 1.4 o.o 53 31 92 152 2.8 5.7 o.o 46 29.2 238 0 o.o o.o o.o 5 29.1 44 19 1. 6 o.o o.o 5 28 6 22 0.3 o.o o.o 53 26 12 0 0.3 0.1 0.0 56 25 0 5 o.o .. o.o o.o 53 24 1 0 o.i 0.3 o.o 55 23 13 26 0.·4 0.3 o.o 56 22 38 48 3.9 1.1 0.3 55 21 12 10 1.1 1. 0 0.2 54 20.5 90 306 0.3 0.4 0.7 50 20.43 82 300 2 .• 9 o.o o.o 47 20.42 171 223 4.3. . o. 2 o.o 46 20.41 243 833 5.6 0.2 o.o 47 20.3 66 101 6.0 0.3 o.o 50 20.2 8 0 1.1 0.0 o.o 51 19.5 21 3 . o. 1' o.o o.o 49 19.4 37 14 0.4 o.o 0.0 53 19.3 39 69 0.4 0.3 0.6 51 19.2 59 83 0.2 L3 0.1 51 19.1 28 6 0.1 0.5 o.o 51 18 0 0 o.o (1.1) o.o 1 17 0 0 0.0 o.o o.o 1 12 0 0 o.o o.o o.o 1 11 0 0 o.o o.o 0.0 1 10 43 0 0.5 o.o o.o 4 8 169 207 19.0 0."0 o.o 6 7 62 113 4.5 o .. o o.o 4 6 33 0 o.o o.o 0.0 3 5 173 24 9.3 o.o 0~0 3 3 42 0 o.o o.o 'o. 0 2 2 28 6 1. 5 0.0 o.o 2 ------~------37 2,011 2,868 68.8 17.6 4.3 1,211 ======... 12 Table 3. Census average of each study plot for black-legged kittiwakes, common murres, and pelagic cormorants at Cape Peirce, May 21 to August 30, 1986. ======Study Plot Species BLKI COMU PECO 43 59 40 1 42 19 105 0 41 10 16 0 40 30 89 0 39 18 19 0 31 78 171 4 29.2 105 161 1 29.1 8 13 1 28 3 11 0 27 46 0 0 26 15 0 0 25 0 ' 17 9 24 2 0 1 23 15 25 2 22 31 44 1 21 24 30 1 20.5 75 200 1 20.4 332 948 16. 20.3 45 39 5 20.2 15 0 1 19o5 19.4 12 0 0 19.3 0 128 0 19.2 33 52 0 19.1 .13 0 0 18 0 0 7 17 0 1 1 12 0 0 0 11 0 0 0 10 8 91 157 8 7 36 116 6 .6 10 0 1 5 54 45. 6 3 14 1 .14 1 0 0 3 ------~------Total 1,218 2,446 92 ======~======i • A 13 Table 4. Nesting Att~mpts 43 59 0 53 0 77 (l 61 1 42 11 1 10 0 17 0 8 2 39 29 0 24 0 29 0 21 0 31 99 0 95' (l 95 0 13 1 26 10 0 14 0 22 0 15 0 22 2 2 19.5 2 0 19.4 1 1 19.2 5 1 ====== Table 5. Productivity parameters and results of black-legged kitti~akes at Cape Peirce, 1984-1987. ======~======~ Parameter Year 1984 1985 1986 1987 Clutch· size " 1.35 1.40 1.22 Nest attempts 272 260 221 128 Nests w/eggs 36% 28% 51% 42% Mean hatching date 7-28 7-3 7-22 Hatching s~ccess 0.01 0.32-0.64 0.49 Fledging SL\CCeSS 0.50 0.01 0 0.25 Repr·odLtcti ve success 0.01 0.01 0 0. 15 Pr·odL\cti vi ty 0.01 0.01 0 0.06 ======Clutch size = number of eggs per nest w/eggs. Hatching success = eggs hatched per eggs laid. Fledgling success = chicks fledged per eggs hatched. Reproductive success = chicks fledged per nests w/eggs. Productivity = chicks fl~dged per nest attempt. ------ 14· Table 0·· Productivity parameters and results of pelagic cormorants at Cape Peirce, 1986-1987. ======Par·ameter Year 1986 . "1987 ---·------~------Clutch size 2.26 2.34 Nest attempts 44 40 Nests w/eggs 70% 87.5% Mean laying date 5-30 6-5 . Mean hatching date 6-27 7-2 Hatching success 0.67-0.73 0.98 Mean fledging date 7-26· 8-1 Fledging success 0.40 0.71 Reproductive success 1.55-1.71 1.63 Pr·oducti vi ty 1. 09-1.20 1.43 ~======~======See Table 5 for description qf parameters. / ... .. : (• 15 APPENDIX A. Total number of black-legged kittiwakes for all study plots, 1987. BLACK ·LEGGED KITTIWAKES {All STUDY PLOTS) 2.& 2.11 .···· 22 2 1.8 (I) ...... tG ~ 'U• UJ c tal m II ") 1.2 0 ~ .t:. :J ...... 1 z o.s 0.6 0,11 0.2 l 0 A c II 0. :> ) :I • '") ., co• ~ I ( I I I i 1.0 ':t Ill ll) N ID " (V r 9 DATE .. 16 APPENDIX B. Total number of common murres for all study plots~ 1987. COMMON MURRES G,------~(ML_·_s_ru_o_~_P_uns~~)------~ 0 c 4 J ..,3 ;) ~ .., ( I I I I Ill II) :t ,..Ill N N " DATE ·' ' ' 17 APPENDIX C. Total number of pelagic cormorants for all study plo~~, 1987. PELAGIC CORMORANTS (ALL STUDY PLOTS) 90 80 70 60 (1'1 1¥ so ..... m ::e :z= ~0 30 ...... tU !• 10 ~ 0 c II Q. ~ -.,J 3 i ., ·( r.o• I 'I I I I Ill Ill ~ Ill VI a ·N N r ·o DATE ... ~ -. 18 APPENDIX D. Total number of horned puffin§ for all study plots, 1987. · ! - • < • • 19 APPENDIX E. Total number of tufted puffins·for all study pl<;>ts, 1987. TUFTED PUFFINS (All STUDY PLOTS) 12 11 - 10 - 9 - II I .v (I) 8 - • a:: w 7 - m 6 - ~ • . ~ ':J 5 - i ~ ·z 4 - ii 3 - 2 - r 1 - ~ v ~. ~ 0 'I Vu~ c: II -·Q. ;:) ) :I ., ., ( aJ• I I . I I Ill 't ID 411 N N ,.. 0 DATE .. ' ...... I • • ..., • ··~ • c • "' • 20 BIBLIOGRAPHY Her·ter·, D.R. and Higgins, B. <1986) Seabird observations at Cape Peirce, summer 1985. Unpublished report to the U.S. Fish and Wildlife Service, Dillingham, Alaska. Higgins, B.M. (1985) Seabir·d abundance and behavior· on Cape Peirce, Alaska--1985. Unpublished report to the U.S. Fish and Wildlife Service, Anchorage, Alaska. Johnson, S. R. ( ed. ) <1985) Population, estimation, productivity and food habits of nesting seabirds at Cape Peirce and the Pribilof Islands, Bering Sea, Alaska. Unpublished report by LGL Ecological Research Associates for the Minerals Management Service, Anchorage, AK. pp. 191-240. Lloyd, D.S. (1985) Breeding performance of kittiwakes and murres in ·relation to oceanographic and meteorologic conditions across the shelf of the southeastern Bering Sea. Master of Science Thesis~ Univ. of Alaska, Fai r·banks. Petersen, M.R. and Sigman, M.J. · (1977) Field studies at Cape Peirce, Alaska--1976. Unpu~lished report to the U.S. Fish and Wildlife Service, Anchorage, and to NOAA-OCSEAP, guneau, Alaska. Van Hul steyn, L. and Kavanaugh, K. <1987) F'opul ati on and productivity surveys of black-legged kittiwakes, common murres, and pelagic cormorants at Cape Peirce, Alaska, summer 1986. Unpublished report to the U.S. Fish a~d Wildlife Service, Dillingham, Alaska . • . Many nests are destroyed by predation, thus the number of nests will decline as the breeding season progresses. The first kittiwake egg. was observed on June 24, and egg laying was complete by approximately. July 20. Of the 128 nests observed, at least 42% contained eggs. The remaining nests either had no eggs, or the adults incubated so tightly that nest contents were never seen. The percentage of . nests with eggs in 1987 is comparable to those of previous years
. Of the 54 nests that were known to contain eggs, 42 had one egg, and 12 had two eggs, giving an average of 1.22 eggs per nest. No nest was ever seen containing more than two eggs or more than one chick. The clutch size decreased slightly, but not significantly, from 1.40 in 1986
gull~ ate the eggs on the ledges. Researchers never witnessed predation on chicks in 1987, although they have in previous years. Researchers lea~ned to approach .the study plots quietly and slowly to minimize disturbance, but murre productivity may still have suffered despite these efforts. Red foxes occasionally preyed on adult murres on the higher, more accessible cliff ledges.
. Since cormorants· do not nest at the same sites every year, the number of adults_ at the stud~ plots is likely to vary considerably between years. Tables 2 and 3 show the study plot popu~ations of 1986 and 1987. · The cormorants were already on the nest sites and nest building when volunteers arrived on May 19. Egg-laying was assumed to have started by the end of May, when broken eggs were found on the cliffs. Of the 40 nests observed, 87.5% were known to contain eggs
. Factors contributing tb the low productivity of murres in 1987 were predation on eggs and chicks by ravens and gulls. Ravens appeared to prey more on murre eggs than kittiwake and cormorant eggs~ because murres most easil.y abandoned their nest site~. Even after researchers learned to approach the study plots quietly, the adult murres sometimes were scared from the study plots. In contrast to 1986, however, no predation on ~ggs or chicks was observed as a direct result of the presence of resear·cher·s. More time should be allowed for scanning for murre eggs and chicks than for the other two species, since they are the most difficult to detect. As recommended in 1986, a time-lapse camera at the productivity plots would aid in determining dates of egg laying, hatching, and fledging. Individual eggs and chicks might be identified easier, as well as breeding adult pairs, and productivity parameters would be more accurate.