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STATUS OF LEDGE-NESTING SEABIRDS AT MONITORING SITES IN THE ALEUTIAN ISLANDS, ALASKA IN SUMMER 1989
G. Vernon Byrd and Hector D. Douglas
Key words: northern fulmar, red-faced cormorant, pelagic cormorant, black-legged kittiwake, red-legged kittiwake, common murre, thick-billed murre, Buldir I., Agattu I., Amukta I., Aiktak I., Aleutian Islands, populations, productivity
u.s. Fish and Wildlife Service Alaska Maritime National Wildlife Refuge Aleutian Islands Unit Box 5251 Adak, Alaska 98791
December 1989
FWLB 1116 ARLIS Alaska Resources Library & r~'""'118tf Anc• . . ·' on Sernces .;j. '"·e·. 'udska TABLE OF CONTENTS Page Abstract •..•• ...... 1 Introduction ...... 2 Methods •••••.••••.••• ...... 4 Results and Discussion ...... 11 Northern Fulmar •••..•.•.•••...... 11 Cormorants ••.••••. . ... 12 Populations •• ...... 12 Phenology ••••...... 12 Productivity ...... ~ .. 14 Black-legged kittiwake...... 16 Populations at Agattu •••••• ...... 16 Populations at Buldir...... 16 Populations at Amukta. ... 16 Distribution and Habitat Use at Buldir 22 Phenology at Agattu ••••• .... 24 Phenology at Buldir ••...... 24 Productivity at Agattu ...... 26 Productivity at Buldir 26 Productivity at Amukta ...... 26 Red-legged kittiwake .•• ...... 30 Population ...... 30 Phenology •• ...... • ••••• 30 Productivity ..••• ...... 30 Common and thick-billed murres. ... 35 Populations at Agattu .••• • • • • • • ...... 35 Populations at Buldir...... 35 Populations at Amukta •• ...... 35 Populations at Aiktak...... 35 Phenology at Agattu •••• ...... 42 Phenology at Buldir ..• ...... 42 Productivity at Agattu ...... 42 Productivity at Buldir ...... 42 Acknowledgements ...... 45 Literature cited •••••••••• ...... •... 47 Appendicies .••..••• ...... •• A-1
(Y) c.o,...... ARLIS 1.0...... ,...... Ala:.: ka R~sources g Abrar'. {(; Information SerVices 0 An cr._· 1.0 1.0,...... (Y) i (Y) LIST OF TABLES No. Title Page
1 Summary of cormorant nest counts at "Kittiwake Lane" (Slide Mountain Colony), Buldir Island, Alaska in different years •••••.•••••••••••••••••••••••••••••••••.• 13
2 Reproductive performance of red-faced cormorants at . Agattu in 1989...... 15
3 Results of black-legged kittiwake population counts on index plots at Agattu Island, Alaska in 1989 (9 plots, Aga Cove; 7 plots, Island Cove) •••••••..•••••• 17
4 Results of black-legged kittiwake population counts on index plots at Buldir Island, Alaska in 1989 ••••••••• 18 5 summary of black-legged kittiwake nest counts at "Kittiwake Lane" (Slide Mountain Colony), Buldir Island·, Alaska in different years. • • • • . • • • • • • • • • • • • • • . • • 19
6 Summary of kittiwake nest counts at Middle Rock, Buldir Island, Alaska in different years ••••••••••••.... 20
7 Comparison of black-legged kittiwake counts on index plots at Buldir Island, Alaska in 1988 and 1989 •.••••••• 21
8 Counts of black-legged kittiwakes at Amukta Island, Alaska in 1989...... 23
9 summary of black-legged kittiwake clutch sizes in the western Aleutian Islands in different years ••••••••.•••. 27
10 Reproductive performance of black-legged kittiwakes in the western Aleutian Islands in 1988 and 1989 •••••••• 28
11 Comparison of black-legged kittiwake reproductive parameters at Aga Cove, Agattu Island, Alaska •.••••••••• 29 12 Population counts of red-legged kittiwakes on index plots at Buldir Island, Alaska iri 1989 •••••••••••••••••• 31 13 Summary of red-legged kittiwake nest counts at "Kittiwake Lane" (Slide Mountain Colony), Buldir Island, Alaska in different years ••••••••••••••••••••••. 32
14 Reproductive performance of red-legged kittiwakes at Buldir Is., Alaska in 1988 and 1989 •••••••••••••••••• 34
15 Results of common murre population counts on index plots at Agattu Is., Alaska in 1988 and 1989 •••••••••••• 36 ii LIST OF TABLES (continued) No. Title Page 16 Summary of murre population counts at Agattu Island, Alaska in different years ••••••••••••••.••...... 37
17 Results of thick-billed murre population counts on index plots at Buldir Is., Alaska in 1988 and 1989 •..... 38
18 Summary of thick-billed murre counts at "Kittiwake Lane" (Slide Mountain Colony), Buldir Island, Alaska in different years •...•••••.•••..••••...•••...... 39
19 Summary of murre counts at Middle Rock, Buldir Is., Alaska in different years .....•••••••••••••.•••••••••.•. 40
20 Counts of murres on Amukta Island, Alaska in 1989 ...... 41 21 Reproductive performance of common murres at Agattu Is., Alaska in 1989 ...... 44
22 Reproductive performance of thick-billed murres at Buldir Is., Alaska in 1988 and 1989 •..••...... 46
iii LIST OF FIGURES No. Title Page 1 Map of Aleutian Islands showing islands where ledge-nesting seabirds wer~ monitored in 1989 ••••••••••• 3
2 Map of Agattu Island showing locations of study plots for ledge-nesting seabirds in 1989 •••••••••••••••• 6
3 Map of Buldir Island showing the location of study plots for ledge-nesting seabirds in 1989 (population plots inside, productivity plots outside parentheses). Asterisk shows the location of nesting fulmars in the mid-1970's...... 7
4 Map of Amukta Island showing the location of study areas for ledge-nesting birds in 1989 ••••••••••••••••••• 8
5 Distribution of laying and hatching dates for black legged· kittiwakes at Buldir and Agattu islands in 1989 ...... 25
6 Distribution of laying and hatching dates for red- legged kittiwakes at Buldir Island in 1989 •••••••••••••• 33
7 Distribution of hatching dates for murres at Agattu and Buldir Islands in 1989 •••••••••••••••••••••••••••••• 43
iv LIST OF APPENDICIES No. Title Page 1 Reproductive performance of red-faced cormorants on index plots at Agattu Island, Alaska in 1989 ...... A-1
2 Black-legged .kittiwake population counts on index plots at Agattu Island, Alaska in 1989 •.....•••..•..... A-2
3 Black-legged kittiwake population counts on index plots at Buldir Island, Alaska in 1989 •.•••••.•••.•.... A-3
4 Counts of black-legged kittiwakes ~n index plots at Main Colony on Amukta Is., Alaska 1n 1989 ...•.••.•..... A-4
5 Reproductive performance of black-legged kittiwakes on index plots at Agattu Island, Alaska in 1989 •.•••••. A-5
6 Reproductive performance of black-legged kittiwakes on index plots at Buldir Island, Alaska in 1989 ...... A-6
7 Red-legged kittiwake population counts on index plots at Buldir Island, Alaska in 1989 ••.••••.•.•.•.•..•.•... A-7
8 Reproductive performance of red-legged kittiwakes on index plots at Buldir Island, Alaska in 1989 •....•.. A-8
9 Common murre population counts on index plots at Agattu Island, Alaska in 1989 ••.••••••..•••••••••.•.•.. A-9
10 Thick-billed murre population counts on index plots at Agattu Island, Alaska in 1989 ••••.••••••••••••••.•.. A-10
11 Thick-billed murre population counts on index plots at Buldir Island, Alaska in 1989 .•.•...••••.••.•.••..•. A-ll
12 Counts of murres on plots at "Main Colony" Amukta Is., Alaska June 28-July 7, 1989 (all counts made between 1200h-1630h) . • • . . • ...... • • • • . . • . . . • ...... A-12
13 Reproductive performance of common murres on index plots at Agattu Island, Alaska in 1989 .••••...•••...... A-13
14 Reproductive performance of thick-billed murres on index plots at Buldir Island, Alaska in 1989 .••••.•••.. A-14
v ABSTRACT Seabird monitoring in the Aleutian Islands durin9 summer 1989 focused on a guild of ledge-nesting species including northern fulmar (Fulmarus glacialis), cormorants (Phalacrocorax spp.), kittiwakes (Rissa spp.), and murres (Uria spp.). The main study sites were Agattu and Buldir islands in the western Aleutians, but additional data were obtained in the central (Amukta I.) and eastern (Aiktak I.) Aleutians.
Results of Eonitoring in 1989 suggest that fulmars continue to expand their nesting area at Buldir. In contrast red-faced cormorants (Phalacrocorax urile) may have declined at Buldir since the mid-1970's. Red-faced cormorants apparently had relatively poor reproductive success at Agattu in 1989. Black-
legged (Rissa tridactyla) and red-legged kittiwakes (~ brevirostris) have increased at Buldir since the mid-1970's, but both species had poor reproductive success there in 1989. Interestingly, black-legged kittiwakes had better success at Agattu than at Buldir. Counts of black-legged kittiwakes at Agattu and Amukta in 1989 were similar to earlier years. Common murres (Uria aalge) appear to be increasing. slightly at Agattu since the late 1970's, and thick-billed murres (Uria lomvia) have increased during the same period at Buldir. Murre counts at
Amukta were slightly higher in 1989 than in 1982, but at Aiktak less than 200 murres were present on cliffs' in 1989 that had contained 13,000 in 1980! Presumably this represents a seasonal absence not a population crash.
'·"'" 1 J
INTRODUCTION During the summer of 1989 a long-term seabird monitoring project continued in the western Aleutian Islands at Buldir and Agattu. The primary objective of the 1989 field surveys was to continue monitoring a system of plots, most delineated in 1988, from which data can be obtained to estimate trends in populations and reproductive success of ledge-nesting seabirds in the western Aleutians. Plots delineated during surveys prior to 1988 were also included in this study.
The target of the monitoring effort was a guild of seabirds which nest on cliff ledges and feed primarily on fish. The main species in the western Aleutians are northern fulmar ( Fulmarus glacialis) , pelagic cormorant (Phalacrocorax pelagicus) , red faced cormorant (Phalacrocorax urile) , black-legged kittiwake (Rissa tridactyla), red-legged. kittiwake (Rissa brevirostris),
common murre (Uria aalge), and thick-billed murre (Uria lomvia). Recent concerns about declines in fish-eating seabirds in the north Atlantic and in the southeastern Bering Sea prompted us to focus on this guild because its species have been adversely affected by food shortages caused by commercial fishing, entanglement in gill nets, and possibly ingestion of plastic and other marine debris.
The primary sites chosen for long-term monitoring in the western
Aleutians, Agattu and Buldir islands (Fig. 1), provide a contrast
in food webs. The main prey of piscivorous seabirds around
2 IZEMBEK NATIONAL ALEUTIAN ISLANDS UNIT WILDLIFE REFUGE ALASKA MARITIME NATIONAL WILDLIFE REFUGE Amok I.~ Cold Bay ALASICA Unima27:1. 0 80 0 80 Shishaldin 9372x • « Dutch Harb:~ ~ Sedanka I. ~ Attu I. Unalask~-.,:;! \:i ~ttu Nizki/Aiaid Is. Umnakf?. 'c.-~~<:f:. 'till NEAR .;. \'<> ISLANDS • Shemya I. o? • oi-- <1 ~ Carlisle I. I ~ Agattu I. Buldir I . ....,. .:-,... •.a . "1"-f "+ / , • Chuginadok I. • 1<: .• v . · Little Seguam I. •,. Yunaska I. QY' S Klska • Sitkin I. Semisopochnoi I. ~ ~AtkaSegvi'lo . ~ \S\..p.\'IO~ol..ll-l"tP.\t-1 All! ' 0 Tanaga I. Kanaga I. O <::::::::;::::P 111 y:ol.lf' ~ "'as 11 ~-., . Ra~. ~AIVD.s • ~ttd) ~.,.. Atka I. Amlia ~os ~ . . Amc'hitka I~ ' ~d:: I. ,, Figure 1. Map of the Aleutian Islands showing islands where ledge-nesting seabirds were monitored in 1989. Agattu is apparently sand lance (Ammodytes tobianus), similar to that of colonies near the coast of mainland Alaska (Springer and Byrd 1988). In contrast, Buldir is more oceanic in character. The prey of seabirds is much more diverse at Buldir, sand lance being only a minor ingredient in seabird diets in summer (A. Springer pers. comm.). In a general way these two colonies are examples of two major "types" of seabird nesting areas in Alaska. Data from the western Aleutian islands provide comparisons with similar infermation about these species of seabirds at other selected monitoring sites in the Aleutians (e.g., Amukta and Aiktak, Fig. 1), and elsewhere on the Alaska Maritime NWR (i.e., Chukchi Sea, Bering Sea, Alaska Peninsula, and Gulf of Alaska). Contrasts among sites will provide a better understanding of processes in the marine ecosystem, and help to suggest causes for observed population trends and fluctuations in reproductive performance. METHODS Surveys were conducted by teams of observers stationed at Buldir, Agattu, and Amukta for extended periods and by two observers who spent a week on Aiktak from late May through mid-August. As in 1988 most observations were made from land on a series of plots delineated in prior years (Byrd and Climo 1988). Slightly different types of plots are used for monitoring population trends than for monitoring reproductive success. The former was 4 accomplished from any stable vantage, above or below, affording unobstructed views of birds, whereas for.productivity monitoring, plots had to be relatively close (i.e., within 50 m) and viewable from above so that nest contents could be determined. Data Collection For population monitoring, birds were counted on designated cliffs (Figs. 2-4) on at least 5-7 days (depending on scheduling and weather) during the mid-incubation to early chick-rearing part of the-·reproductive cycle. All plots within an area were usually surveyed on each count day between 1100-1700 h, a window in which attendance at cliffs is least variable. Cliff segments included within the population survey areas usually contained 100-500 birds per plot, and count areas included some parts without birds to allow for future expansion. All plots were photographed and boundaries were drawn on prints. Boundaries of plots surveyed from beaches were marked with rock paint, and observation points of plots viewed from above were marked with reinforcement bar. At each visit birds on plots were counted at least twice or until counts clustered within 5% of each other. The average was used for the daily count. Plots were not surveyed on days when winds exceeded 25 mph. Individual birds were tallied for all species, and nests (a structure to which vegetation had been added in the current year) were also counted for cormorants and kittiwakes. 5 AGATTU ISLAND KRUGI.O I 1'0 INT McDONALD COVE WEST COVE / Population Plots 74175,21,22,25-27 AGA LOVE • • GOOSE CREEK BEACH . ProductJ..VJ.ty CABIN "-..... Plots 20-29 COVE ~ AGA COVE TOWER lsl~CAPE SABAK 0 5 ltlKm Population Plots 4-17 Productivity Plots 1-18 ISLAND COVE Figure 2. Map of Agattu Island showing locations of study plots for ledge-nesting seabirds in 1989. BUi.DiR iSLAND, ALASKA II/I ~ ..[1 lDCl Norlhw<>al Point Kittiwake ,r,. ?.-: L ane . '-~~~,;~ PACIFIC The OCEAN Dip ... Scole I:25,000 S ovthea U Point ==~r~~~~~~==~~~~~~~~~~~~~====~~~~·-~ SOUin POUlT C:OlliYO'U• lllflfl"v•\ 500N. Figure 3. Map of Buldir Island showing the location of study plots for ledge-nesting seabirds in 1989 (population plots inside~ productivity plots outside parentheses). Asterisk shows the location of nesting fulmars in the mid-1970's. 4 ,'[[J :!fl -'[!JJ I Lll I ;[[j Ilrn I I:[]]; :JJ JI y.~ 1: Kittiwake--~~~ I Colony 8 Photographs and drawings were used to keep track of individual numbered nests for productivity monitoring. Cliff plots usually contained from 20-40 nest sites. At Buldir we had one major kittiwake colony with no vantage points from above, so we used a mirror on an extension pole to see into nests. This latter method causes some disturbance since birds are temporarily flushed from nests, but kittiwakes return almost immediately after being flushed so disturbance is minimized. Reproductive. performance and nesting phenology were tracked by viewing nests at regular intervals (3-5 days). It was frequently not possible to see the contents of a murre site because the birds remained motionless for long periods of time. We used distinctive behavior (e.g., wings held over ba~k so that tips did not cross, tail down, back slightly humped) to indicate that a murre was incubating. Because it is possible to misinterpret such posture, we used the convention that a site had to have a bird in 11 incubating posture" on at least two consecutive checks to consider the site as having an egg. In a similar fashion wing mantling was used to indicate that a murre had a chick. Data Analysis To summarize population data for each species we averaged replicate counts on the system of monitoring plots. Comparisons were made with previous data by t-tests when only 2 years with replicate counts were compared. 9 ) Determination of the fate of eggs and chicks was not always straightforward because we visited nests only every 3-5 days (occasionally less frequently). As a result it was necessary to adopt some conventions for consistency in interpretation. For cormorants it was especially difficult to determine when chicks fledged because cormorant chicks began to wander away from their nests to other ledges before they could fly. We did not usually know the age of cormorant chicks because many had already hatched before we began observations. So we decided to consider as fledged, red-faced cormorant chicks that were still alive as of July 22, the period when fledging became ubiquitous. For black legged and red-legged kittiwakes we assumed fledging if chicks disappeared after they had attained ages of 36 days and 32 days respectively. Kittiwake chicks at least 24 days of age at our last check were considered to have a low probability of mortality. We considered these individuals fledged. We also adopted the convention that murre chicks fledged if they were at least 15 days old (see Byrd 1986 and Byrd 1989) when they disappeared from the cliffs, or were at least 11 days old at the last check in mid or late August. We considered that murre chicks at least 11 days of age would have a low probability of mortality (prior to fledging), and this is borne out by our data. Estimates of reproductive success were made by using plots as sample units and letting the averages for a plot be the sample observations. Ratio estimation procedures were used to estimate overall means and variances (see Byrd 1989). This approach was 10 employed rather than using an individual nest site as a sample unit since nests physically located close together may share a common fate and data are therefore not independent. RESULTS AND DISCUSSION Northern Fulmar No fulmars were observed at Agattu. At Buldir, the main concentration of nesting birds is still at Amphipod Hill and East Cape, where it was confined in the mid-70's (Fig. 3). Unfortunately, this area is inaccessible to observers on a regular basis, preventing detailed monitoring efforts. However it appears that fulmars may be continuing to extend their range at Buldir (Byrd and Day 1986, and Byrd and Climo 1988). In 1989 northern fulmars and fulmar nest sites were observed further northwest and southwest of East Cape then noted in 1988. In 1988, at least 20 nesting fulmars were found on the south side of Buldir as far southwest as productivity plot 31, and a single nest was seen farther southwest at plot 33 (Fig. 3). In 1989, about 30 fulmars were observed above population plot A at the Dip (at least 100 m farther southwest of East. Cape than plot 33) . Furthermore, birds were again present near plots 31 and 33 (3 on plot 32 and up to 6 on plot 36). Ten previously occuppied thick-· billed murre sites were abandoned at plot 36 on July 21, and the observer attributed this to the disturbance by subadult northern fulmars prospecting for nest sites. On the north side of Buldir in 1988, fulmars were frequently seen in scrapes above cliffs and standing above cliffs as far northwest as the east end of the Kittiwake Lane plots. In 1989, we noted one fulmar nest each at Kittiwake Lane population plots 15 and 16 and two fulmars standing above plot 17 (these are the easternmost plots and represent a slight expansion from 1988). Cormorants Populations--We counted 52 pelagic cormorant nests along the north shore ~f Buldir Island and four more nests at Middle Rock. The greatest concentration of nests was east of Rubythroat Creek along the base of Slide Mountain near Petrel Valley. Only one cormorant nest was seen at Kittiwake Lane in 1989, fewer than in previous years (Table 1). It is difficult to interpret differences in counts on fixed plots among years since cormorants are notorious for shifting nesting locations. However, subjective observations indicate that particularly red-faced cormorants may have decreased since the 1970s (Byrd pers. obs.). Only seven nests of red-faced cormorants were noted within study areas at Buldir in 1989 and few individuals were seen in transit by boat. In contrast, we frequently saw pelagic cormorants on boat trips. For example, nearshore boat transect on August 15 from the east end of Kittiwake Lane to North Rock, revealed 52 adults, 14 immatures, and 5 fledgling pelagic cormorants. Phenology -- Pelagic cormorants at Buldir began fledging by mid-August, but the peak was some time after August 20. Red- Table 1. Summary of cormorant nest counts at "Kittiwake Lane" (Slide Mountain Colony) 1 Buldir Island, Alaska in different years. a b b Segment 1974 c 1975 1988 1989 (Plot) PECO RFCO PECO RFCO PECO RFCO PECO RFCO 1 (15) 0 3 0 0 0 0 2 (16) 0 5 0 1 1 0 3 (17) 0 11 0 0 0 0 4 (18) 0 7 0 0 0 0 5 (19) 3 4 0 0 0 0 6 ( 20) 1 3 0 0 0 0 7 (21) 3 0 0 0 0 0 8 (22) 2 0 0 0 0 0 9 ( 2 3) 0 0 0 0 0 0 10 (24) 0 0 0 0 0 0 11 (25) 0 0 0 0 0 0 12 (2 6) 0 0 0 0 0 0 13 (27) 0 0 0 0 0 0 14 (28) 0 0 1 0 0 0 Total 8 29 9 33 1 1 1 0 a Original plot codes were 1-14, but in 1988 they were renumbered 15-28 b from Byrd (1978)- figures, are from single counts taken on 6 July 1974 and 8 July 1975 c PECO = pelagic cormorant, RFCO = red-faced cormorant 13 faced cormorants fledged earlier. At Agattu, red-faced cormorants had begun to fledge by July 22 and the peak of fledgling appears to have been soon thereafter. Hatching must have occurred primarily from mid- May to early June, and laying must have commenced in mid-April. The timing of nesting events was similar between 1988 and 1989 and likewise in 1978 (we assumed incubation and nesting periods were similar to those recorded for the species in the Pribilof Islands--incubation 31 days, nestlings 59 days-- Hunt et al. 1981). Productivity -- Broods in successful (i.e., nest where at least one egg hatched) red-faced cormorant nests averaged 2.1 chicks at Agattu in 1989 (Table 2), down from 3.1 in 1988 (Byrd and Climo 1988). Red-faced cormorants experienced poor chick survival in 1989 at Agattu; only 24% of the chicks fledged and only 27% of nests produced one or more fledglings (Table 2, Appendix 1) . There was no obvious reason for the relatively low red-faced cormorant productivity at Agattu in 1989. Few dead chicks were seen in nests. Predation by common ravens may have been a factor. Pelagic cormorant broods in four nests at Buldir averaged 2.75 in 1989, and six nests at Agattu had 2.0 chicks/nest. Three of the six nests at Agattu produced at least one fledgling. 14 ------~------ Table 2. Reproductive performance of red-faced cormorants at Agattu in 1989. Measures of Success a b c d Location Statistics Brood Size Fledgling Success Productivity e f Agattu n 42 3 3 X 2 •. 14 .24 • 27 s .78 • 1 0 • 1 6 90% C.B. .28 .42 • 6 5 a statistical abbreviations: n=sample size, x-mean, s=standard deviation, 90% C.B.=90% confidence bound b maximum number of chicks seen in nests with ~ 1 chick c no. of fledgling/successful nest (one where an egg hatched) d fledglings per maximum number of chicks seen e chicks f plots (i.e. clusters of nests) Black-legged Kittiwake Populations at Agattu--We estimated that 1 1 312 black-legged kittiwakes and 766 nests were present on plots at Aga Cove in July 1989 (Table 3 1 Appendix 2). At Island Cove an average of 1 1 560 birds and 794 nests were estimated to have been present (Table 3 Appendix 2). These counts were slightly lower than in 1988 (Byrd and Clime 1988). Populat~ons at Buldir--Replicate land-based counts of black legged kittiwakes and nests were made at three areas on Buldir1 and a single boat-based count was made at Middle Rock in July 1989 (Table 4 1 Appendix 3). Black-legged kittiwake populations have increased substantially over the previous 14 years both in the numbers of nests and the extent of nesting area at both Kittiwake Lane and Middle Rock (Tables 5 and 6). The number of kittiwakes present on index plots at Kittiwake Lane were similar in 1988 and 1989 (p > 0.1) 1 but numbers increased at the Dip (p < o .1) and apparently at Middle Rock (lack of replicates precludes testing for differences) (Table 7). Interestingly 1 fewer nests were present (p' s < 0. 1) at all the areas where replicate counts were made in 1989 than in 1988. Apparently a lower percentage of birds present constructed nests in the latter year. Populations at Amukta.--About 80 black-legged kittiwakes occupied index plots at the "Main Colony" and roughly 95 more 16 Table 3. Results of black-legged kittiwake population counts on index plots at Agattu Island, Alaska in 1989 (9 plots, Aga Cove; 7 plots, Island Cove). Area Count Aga Cove Island Cove a 1 1233(754) 1258(770) 2 104 0 (85 0) 1564(863) 3 1281(760) 1495(790) 4 1392(767) 1476(834) 5 1464(788) 1515 ( 7 8'7) 6 1265(780) 1791 (774) 7 1184(774) 1705(764) 8 1303(750) 1677(772) 9 1407(769) 10 1367(764) 11 1500(760) b Statistics n 1 1 ( 1 1 ) 8 ( 8) X 1312.4 (765.8) 1560.1 (794. 2) s 132.9 (11.4) 114. 5 (23.6) 90% C.B. 72.5 ( 6. 2) 76.7 (15.8) a nest counts in parentheses b statistical abbreviations: n=sample size (replicate counts), x=mean, s=standard deviation, C.B.=confidence bound 17 Table 4. Results of black-legged kittiwake population .counts on index plots at Buldir Island, Alaska in 1989. Area a b c Count DiQ KLE KLW tUddle Rock d 1720 (1367) 2729 (1838) 2085 (1247) 2056 (1041) 2 2570 (1381), 2040 (1720) 1666 (1093) 3 2452 (1453) 2687 (1817) 1909 (1133) 4 2561 (1382) 2922 (1742) 2329 ( 1123) 5 2754 (1535) 2864 (1752) 1832 ( 1106) 6 2515 (1576) e 7 2508 f Statistics n 7 ( 6) 5 ( 5 ) 5 ( 5) 1 (1) ~ X 2440.0 (1449.0) 2648.4 (1773.8) 1964.2 (1140) 2056 (1041) O::J s 306.8 (81.0) 31 6. 1 (45.5) 226.8 (55) 90% C.B. 364.4 (111.3) 529.6 (76.3) 380.0 (92.2) a plots 1-14, A,B,C b Kittiwake Lane East consists of plots 15-18 (segments 1-4) c Kittiwake Lane West consists of plots 19-28 (segments 5-14) d nest counts in parentheses e s~venth count at the Dip includes several plot averages for missing values f statistical abbreviations: n=sample size, x=mean, s=standard deviation, C~B.=confidence bound ------:::-:::::::-::-:::==:::======~--~------:--::-:-=::-:- Table 5. Summary of black-legged kittiwake nest counts at 11 Kittiwake Lane" (Slide Mountain Colony), Buldir Island, Alaska in different years. Year Segment a a b c (Plot2 1974 1975 1988 1989 1 ( 1 5) 137 563 424 2 ( 1 6 ) 133 637 510 3 ( 17) 76 728 568 4 ( 1 8 ) 123 628 271 5 (19) 63 368 237 6 (20) 39 284 180 1 ( 21 ) 24 341 215 8 (22) 5 264 236 9 (23) 0 219 230 10 (24) 0 1 0 9 11 (25) 0 7 5 12 (26) 0 18 1 1 13 (27) 0 15 9 14 (28) 0 18 9 d e e Total 649 600 4100 + 68.3 2914 + 161.2 a from Byrd (1978); figures are from single counts taken on 6 July 1974 and 8 July 1975 b figures are means of three replicate counts taken from 5 July to 2 1 J ul y, 1 9 8 8 c figures are means of five replicate counts taken from 29 June to 16 July d includes 44 Rissa sp. e 90% confidence bound 19 Table 6. Summary of kittiwake nest counts at Middle Rock, Buldir Island, Alaska in different years. Year b b c Area 1974 1975 1984 1988 1989 d e e I 80 (5 RLKI) 177 139 (206) 139 {342) II 33 (3 RLKI) 72 75 (135) 95 {225) III 70 107 150 (241) 120 (175) IV 25 155 94 (210) 60 {97) v 82 (2 RLKI) 107(1 RLKI) 87 (135) 183 (402)+2 RLKI VI 0 50 172 (300) 170 (296) VII 0 0 313 (428) 274 (519) N o Total 360(10 RLKI) 290(10 RLKI) 668(1 RLKI) 1030(1655) 1041 (2056) a see Fig. 3 b from Byrd (1978) c from DeGange and Wood (1984) d red-legged kittiwake nest counts in parentheses included in total counts e number of individual black-~egged kittiwakes in parentheses under 1988 and 1989; no red-legged kittiwakes were noticed in 1988 and only two in 1989. Table 7. Comparison or black-legged kittiwake counts on index plots at Buldir Island, Alaska in 1988 and 1989. ------!BE.~A~------~------a b KLE. ____ K1W THE DIP Middle Roc]S __ ~-=-=·.:::.!:' ~--- _1.9 _8 _8- - - ___1:_.9{..!8:..19:..______----L,=..::_:__ 1988 ____ 1.91!.9 1988 1989 19.§8 1989 c Sample Size 4 (4) 5 (5) 7 (3) 5 (5) 7 (3) 7 ( 6) 1 ( 1 ) ( 1 ) Mean 2769(2556) 2648(1774) 1912(1543) 1 9 6 4 ( 1 1 4'0 ) 2059(1928) 2440(1449) 1655(1030) 2056(1041) Stand.Dev. 105.1(27.0) 316.1(45.5) 164.3(15.4) 226.8(55.0) 197.9(45.5) 306.8(81.0) 90% C.B. 124 (46) 530 (76) 121 (26) 380 (92) 145 (77) 364 (111) ------a 1 Kittiwake Lane East b Kittiwake Lane West c counts of individuals rollowed by counts of nests in parentheses birds were present at the "Kittiwake Colony" in 1989 (Table 8, Appendix 4). The total of about 175 is similar to the estimate of 150 (75 pairs) made in 1982 (Bailey and Trapp 1986). Distribution and Habitat Use at Buldir. --Apparently there are two preferred nesting locations for kittiwakes (and thick billed murres) at Buldir; the East Cape area (including Kittiwake Lane and the cliffs below the Dip) on the east end of the island and outer and Middle rocks off the northwest point of Buldir (Fig. 3). On JUne 161 19891 during a SUrvey Of the north ShOre Of Buldir Island, we noted apparently adequate nesting habitat for black-legged kittiwakes (and thick-billed murres) but no birds were using the areas. Rock faces with potential nesting ledges extend vertically from the beach both east and west of North Rock, apparently formed from early flows of Buldir Eccentric volcano. Similar formations, perhaps of the same origin, are populated by black-legged kittiwakes (and thick-billed murres) on the south side of the island between Peregrine Point and Southeast Point. Southeast Point is the southerly limit of nesting kittiwakes (and murres) in the East Cape colony, while population plots 28 (and 18) are the northerly limits of nesting black-legged kittiwakes (and murres respectively). The Kittiwake Lane/Slide Mountain colony is characterized by red cliffs composed of crumble breccia. Ledges are formed by irregular rocks and boulders that jut out of the cliff face. This habitat 22 Table 8. Counts of black-legged kittiwakes at Amukta Island, Alaska in 1989. Colony Count Main Kittiwake a 1 63 ( 0) 50 (-) 2 88 (0) 139 ( 1 3 ) 3 64 (0) 4 107 ( 1 ) b Statistics n 4 2 X 81 95 s 21 63 90% C.B. 24.8 280.7 a nests in parentheses b statistical abbreviations: n=sample size, x=mean, s=standard deviation, C.B.=confidence bound 23 is interrupted by Gull Slide, a large landslide at the northeast corner of Buldir, but then resumes along the north shore from the base of Slide Mountain as far west as Rubythroat Creek and Petrel Valley. The materials are apparently the same as those used by kittiwakes (and murres) at Kittiwake Lane and kittiwakes regularly fly over this area "to bathe at Kittiwake Lake and to gather moss for nest building material from the steep slopes of Pon. At ·Kittiwake Lane, kittiwakes are found nesting from the base of the cliffs to the top, while at the higher cliffs below the Dip, the upper cliff area is more densely populated and relatively few individuals in sparse colonies are located along the lower cliff. The chief difference between these two areas is that periodic erosion maintains vertical faces and well-defined breccia ledges on the upper cliff, while the lower cliff is often more gently sloping and ledges are) covered with fine materials eroded from above. Phenology at Agattu--Over 90% of the black-legged kittiwake eggs in plots at Agattu hatched between July 6-21 in 1989 (Fig. 5). This timing is slightly later than in 1988 (Byrd and Climo 1988) . Phenology at Buldir--The peak of laying at Buldir was June 16-19 in 1989, and the hatching peak for black-legged kittiwakes 24 Black-legged Kittiwake Laying Dates Buldir Island, Alaska in 1989 Number of Neala 140~~~~~------~ 120 100 80 60 40 20 0 <12 12·15 16·19 20·23 24·27 28·1 2-G 6-9 10-13 14·17 Dates in June and July Black-legged Kittiwake Hatching Dates Buldir Island, Alaska in 1989 Number of Neala 35~--~------~ 30 26 20 . 1G 10 6 2-G 6·9 10-13 14·17 113·21 22·25 26-29 30-2 3-6 Dates In July and August Black-legged Kittiwake Hatching Dates Agattu Island, Alaska in 1989 100 80 eo 40 20 2-5 6-9 10-13 14-17 18-21 22-25 26-29 30-2 3-6 Dates In July and August Figure 5. Distribution of laying and hatching dates for black-legged kittiwakes at Buldir and Agattu islands in 1989. · 25 at Buldir was during the same period as the peak at Agattu (Fig. 5) • Productivity at Agattu--The average clutch layed by black legged kittiwakes at Agattu in 1988 and 1989 was about 1.6 eggs 1 slightly lower than in 1978 and 1982 (Table 9) . Only 2/3 of the pairs of black-legged kittiwakes that constructed nests at Agattu layed at least one egg in 1989 1 down from 80% in 1988 (Table 10 1 Appendix 5). About 7 of 10 nests with eggs had at least one. chick hatch-in 1989 1 similar to 1988 (Table 9). In 1989 about 60% of the chicks fledged 1 up slightly from 47% in 1988. Overall only 28% of the pairs that built nests produced a fledgling in 1989 1 similar to 1988. The only comparison available from years prior to 1988 were for laying and hatching success in 1982 when they were similar to 1988 (Table 11)~ Productivity at Buldir--The estimated average black-legged kittiwake clutch (1.20) at Buldir was much lower than in 1988 (1. 78) 1 and it was lower than at Agattu in 1989 (Table 9). Amazingly only 36% of the pairs that built nests at Buldir layed an egg 1 only 32% of the eggs hatched 1 and less than 45% of the chicks fledged (Table 10 1 Appendix 6). overall only 5 of every 100 black-legged kittiwake nests on plots at Buldir produced a fledgling in 1989 1 down from 27% in 1988 (Table 10). Productivity at Amukta--As far as we could tell 1 kittiwakes failed to produce any young in 1989. 26 Table 9. Summary of black-legged kittiwake clutch sizes in the western Aleutian Islands in different years. a b c Island 1976 1978 1982 1988 1989 d e f Agattu 1. 72 (25) 1.76 (58) 1. 62 (379) 1. 62 ( 391) d g Buldir 1 • 6 1 ( 7 4 ) 1. 78 (462) 1. 22 (220) a from Byrd and Day (1986) b from Early field noted, refuge files c from Forsell and Amborz (1983) d sample size in parentheses e weighted average from two study areas f weighted average from two study areas (Island Cove and Aga Cove) g weighted average from two study areas (Kittiwake Lane and The Dip) 27 Table 10. Reproductive performance of black-legged kittiwakes in the western Aleutian Islands in 1988 and 1989. Heap~ses of_§uccess b c d e f a Laying Hatching Fledging Reproductive Productivity Loca t_!.Q.Q_§!Eti st i..Qs 1.9_88 1282 1988 1.2.!}.2__1.9 § J3- 1282 1288 1ill_ ___L9§_!J ____ j.2§.L_ Agattu n 18 18 18 18 18 1 8 18 18 18 18 X o. 79 0.68 0.66 0.68 0.47 0.60 0.34 0.41 0.30 0.28 90~ C.B. 0. 17 0.08 0. 19 0.08 0.21 o. 1 o1 0. 19 0.09 0.19 0.08 Buldir D 24 24 24 24 24 24 24 24 24 24 X 0.83 0.36 0.80 0.32 0.37 0.44 0.31 0.14 0.27 0.05 90~ C.B. o. 13 0.09 0.14 0. 13 0.17 0.14 0.16 0.08 0.16 0.03 a statistical abbreviations: n:sample size, x=mean, s=standard deviation, C.B.=confidence bound b proportion of nests where 1 ·egg was laid c proportion of nests with > egg where .L chick was seen d proportion of nests With .L chick where .L 1 chick fledged e proportion of nests with ) egg where .L chick fledged f proportion of total nests where l. 1 chick fledged Table 11. Comparison of black-legged kittiwake reproductive parameters at Aga Cove, Agattu Island, Alaska. Year a Parameter 1982 1988 1989 b Laying success 0.84 0.79 0.68 c Hatching success 0.62 0.66 0.68 a from Forsell and Ambroz (1983) b proportion of nests where at least one egg was layed c proportion of nests with eggs where at least o~e egg hatched 29 Red-legged Kittiwake Populations--Red-legged kittiwakes nest only at Buldir in the western Aleutians. In 1989 replicate counts were made in three areas which included approximately 1, 485 birds and 926 nests (Table 12, Appendix 7). The number of birds present was similar to 1988, but only 80% as many nests were present in 1989 compared to 1988 (Byrd and Clime 1988). Counts in 1989 confirm that there has been a substantial increase since the mid-1970's (Table 13). Phenology--About 77% of red-legged kittiwake pairs on plots layed eggs by June 19, and the peak of hatching was July 14-21 in 1989 (Fig. 6). This timing is slightly later than in 1988 (Byrd and Clime 1988). Productivity--No two-egg clutches were observed at Buldir in 1989. Eggs were layed by only 40% of the pairs that constructed nests in 1989 (Table 14, Appendix 8) . About 49% of the eggs hatched, and half of the chicks fledged. Therefore, the overall success rate was about 10% on study plots in 1989, down from 35% in 1988 (Table 14). 30 Table 12. Population counts of red-legged kittiwakes on index -plots at Buldir Island, Alaska in 1989. Colony: Count Di.Q __. Kittl. Lane East Ki ttl. Lane West 1 332(200) 479(354) 409(272) 2 270(160) 678(388) 441(280) 3 513(292) 599(378) 421(303) 4 485(273) 6~8(379) 457(305) 5 498(297) 664(387) 423(304) 6 589(301) 7 441(268) ------"------~------a Statistics n 7 5 5 X 447(256) 608(377) 430(293) s 102(50) 71(12.3) 1 7 ( 1 4 ) 90% C.B. 121 (60) '11 8 ( 21 ) 28(23) a statistical abbreviations: n=sample size, x=mean, s=standard deviation, C.B.=confidence bound 31 Table 13. Summary of red-legged kittiwake nest counts at "Kittiwake Lane" (Slide Hountain Colony), Buldir Island, Alaska in different years. Year Segment a a b (Plot) 1974 1975 1988 1989 c 1 ( 1 5 ) 80 127 95 2 ( 1 6 ) 89 11 0 83 3 ( 1 7) 46 149 125 4 ( 1 8) 49 167 75 5 ( 1 9) 12 52 51 6 (20) 20 . 109 72 7 ( 21 ) 0 49 49 8 (22) 0 56 56 9 (23) 0 46 63 10 (24) 0 1 1 11 (25) 0 0 0 12 (26) 0 0 0 13 (27) 0 0 0 14 (28) 0 0 1 Total Nests 289 296 866±_44.8 671+ 44.0 Total Birds 1 09 0±.173 1 03 8±:14 6 a from Byrd ( 197 8); figures are from single counts taken on 6 July 1974 and 8 July 1975 b figures are means of 3-5 replicate counts + the 90% confidence bound c originally plots were numbered 1-4, revised numbers in parentheses 32 Red-legged Kittiwake Laying Dates Buldir Island, Alaska in 1989 Number of Nests 60 50 40 30 20 10 0 <12 12-15 16-19 20-23 24-27 28-1 2-5 6-9 Dates in June and July Red-legged Kittiwake Hatching Dates Buldir Island, Alaska in 198 9 Number of Nests 2-5 6-9 10-13 14-17 18-21 22-25 26-29 30-2 3-6 Dates in July and August Figure 6,' ·Distribution of laying and hatching dates for red-legged kittiwakes at Buldir Island in 1989. Table 14. Reproductive performance of red-legged kittiwakes at Buldir Is., Alaska in 1988 and 1989. · ----- Measures of Success b c d e f a Laying Hatching Fledging Reproductive Productivity Statistics 1988_j_9Jt9. 1988 1989 1988 1989 1988 1989 1988 1989 n 8 8 8 8 8 8 8 8 8 8 X 0.78 0.40 0.75 0.49 0.58 0.50 0.45 0.25 0.35 0. 1 0 s 0.12 0.07 0. 14 0. 11 0.26 0.08 0.24 0.07 0.21 0.04 90% C.B. 0.23 0 0 13 0.27 0.20 0.33 0.16 0.33 0.13 0.32 0.08 a statistical abbreviations: n=sample size, x=mean, s:standard deviation, · C.B.=confidence bound b proportion of nests where 1 egg was laid c proportion of nests with 1 egg where L 1 chick was seen d proportion of nests with 1 chick where L 1 chick fledged e proportion of nests with 1 egg where L 1 chick fledged f proportion of total nests where 1 chick fledged Common and Thick-billed Murres Populations at Agattu--In 1988 and 1989 counts were made of murres in three locations: Aga Cove, Island Cove, and Karab Cove (Appendices 9 and 10). There were significantly more murres at Aga Cove in 1989 than in 1988, but numbers at Island Cove were similar between years (Table 15) . The only prior data for comparisons at Agattu are for two plots at Aga Cove and one plot at Karab cove. It appears common murres may have increased since 1978, but there is no sugges:tion of increases in thick-billed murres (Table 16) • Populations at Buldir--Thick-billed murres increased (p < 0.1) at study plots on Buldir between 1988-1989 (Table 17, Appendix 11). Comparisons with data for two areas suggest thick billed murres may have increased since the mid-1970's (Tables 18 and 19). Populations at Amukta--The primary monitoring plot ("Main Colony") contained ·about 977 murres in 1989 (Table 20, Appendix 12). One or two counts were also obtained· for the other 5 areas where murres nest on Amukta (Table 20). The total for all areas, (1872 murres) is slightly higher than the estimate of 1700 made in 1982 (Bailey and Trapp 1986). Populations at Aiktak--We used an inflatable boat to view the entire cliff area on the south side of Aiktak. Although 35 Table 1 5 . Results of common murre population counts on index plots at Agattu Is. , Alaska in 1988 and 1989. Aga Cove Island Cove Count 1988 1989 1988 1989 1 1510 1685 1488 1475 2 1628 1416 1615 1539 3 1403 1509 1606 1355 4 1730 1586 1775 1625 5 1387 1538 1568 1666 6 1309 1629 1574 1523 7 1304 1754 1609 1613 8 1720 1418 1466 9 1718 10 1704 a Statistics n 7 10 8 8 X 1467.3 1625.9 1582.0 1533.0 s 162.8 110.8 103.9 1 01 • 6 90% C.B. 129.2 70.0 71.3 69.7 a statistical abbreviations: .n=sample size, x=mean, s=standard deviation, C.B.=confidence bound 36 =--·-~···======--====-·-=-=-=-=-=-======-=-=· ~=-=-=·· Table 16. Summary of murre population counts at Agattu Island, Alaska in different years. a Plot Species 1978 1982 19..!3.? 1989 e (74) TBMO 97 .:!:. 116.8 52 .:!:. 13.9 66 .±. 8.8 COMO 85 .:!:. 66.3 180 .:!:. 1 4. 3 168 .±. 10.5 2 (26) A TBMO 0 .:!:. o.o 0 not counted 0 .±. 0.7 0 COMO 46 .:!:. 3.7 53 54 .±. 2. 1 59 .±. 4.0 B TBMO 0 .:!:. 0.0 1 0 1 .±. 1.3 0 COMU 100 .:!:. 5.4 118 182 184 .±. 11.5 185 .±. 7.2 c TBMU 0 .:!:. 0.0 0 0 0 .±. o.o 0 COHU 38 .:!:. 1.7 35 36 42 .±. 3.0 48 .±. 2.3 D TBHO 1li .:!:. 1.5 12 15 5 .±. 1.1 5 .±. 0.8 COMO 5 .:!:. 0.9 9 9 1 .:!:. 0.7 0 .±. 0.5 Total TBHU 14 .:!:. 1.5 13 6 .±. 2.4 5 .±. 0.8 A-D COHU 188 .:!:. 10.0 215 281 .±. 12.6 292 .±. 27.5 Total TBMU ·- 1li .:!:. 1.5 13 15 5 .±. 1.9 5 .:!:. 0.8 B-D COMO 142 .:!:. 7.2 162 227 227 .±. 11.7 233 .±. 23.5 5 ( 1 9) TBMU 594 .±. 243.8 COHO 2714 .±. 289.0 ALL HU. 2201 .±. 217.8 3308 .±. 286.6 2629 .±. 167.0 All Plots Aga Cove TBMU 170.4 .±. 30. 1 237.5 .±. 27.9 COMU 1467 .:!:. 129.2 1626 .±. 70.0 All Plots f Is. Cove TBMU COMU 1582 .±. 69.7 1533 .±. 71.3 a from Early (unpublished data) plot 1: figures are means and 90~ confidence intervals of two counts made on 28 June and 1 July; from Day et al. (1979) plot 2: figures are means and 90% confidence intervals of counts taken at half hour intervals between 13:00-17:00 for seven replicate counts, 24 June to,6 July; from Day (unpublished data) plot 5: figure is mean and 90% confidence interval of two counts made on 29 June and 1 July b from Forsell and Ambroz (1983); figures are means of counts taken at half hour intervals between 13:00-17:00, 23 June c from Forsell (1983); single count made at approximately 22:00 (BDST) on 11 June d figures are means and 90% confidence intervals of replicate counts (seven for plot 1, six for plot 2, four for plot 5) made from 8 July to 29 July e 1988 plot numbers in parentheses following 1978 plot numbers f no thick-billed murres on comparable plots 37 Table 17. Results of thick-billed murre population counts on index plots at Buldir Is., Alaska in 1988 and 1989. AREA a b Dip KLE Middle Rock Count 1988 1989 1988 1989 1988 1989 1 1913 2229 311 408 681 1480 2 2107 2089 380 440 3 2265 2308 337 490 4 2167 2252 297 452 5 2177 2337 400 355 6 2339 407 c Statistics n 5 6 6 5 1 1 X 2125.8 2259.0 355.3 429.0 681 1480 s 131.7 86.3 46.9 45.4 90% C.I. 125.5 118.6 38.5 75.9 a plots 1-14, A,B,C b Kittiwake Lane East consists of plots 15-18 (segments 1-14) c statistical abbreviations: n=sample size, x=mean, s=standard deviation, C.B.=confidence bound 38 Table 1 8 • Summary of thick-billed murre counts at "Kittiwake Lane 11 (Slide Mountain Colony), Buldir Island, Alaska in different years. Year Segment a a b c (Plot) 1974 1975 1988 1989 ( 15) 20 73 70 2 ( 1 6 ) 43 99 167 3 ( 17) 37 113 125 4 ( 1 8 ) 35 71 67 5 ( 1 9 ) 0 0 6 (20) 0 0 7 ( 21 ) 0 0 8 (22) 0 0 9 (23) 0 0 1 0 (24) 0 0 11 (25) 0 0 12 (26) 0 0 ~ 13 (27) 0 0 1 4 (28) 0 0 d d Total 173 135 355 + 38.5 429 ±. 76 a from Byrd (1978); figures are from single counts taken on 6 July 1974 and 8 July 1975 b figures are means of six replicate counts taken from 5 July to 27 July c figures are means of five replicate counts taken from 29 June to 16 July d mean ±. 90% confidence bound 39 -~ ------~,--· Table 19. Summary of murre counts at Middle Rock, Buldir Is., Alaska 'in different years. a a b Area 1974 1975 1984 1988 1989 c I 170 23 9 ( 31 cor-m) 182 (35 COHU) 306 II 70 69 74 133 III 1 a 69 47 34 IV 0 149 28 1 1 1 v 65 23 0 72 VI 0 0 44 69 VII 0 0 341 740 ' Total 340 (22 COHU) 315 549 (31 COHU) 716(35 COMU) 1480 a from Byrd (1978) b from De Gange and Wood (1984) c common murre counts included in total counts 40 Table 20. Counts of murres on Amukta Island, Alaska in 1989. Colony Count Main______Kittiwake North Pinnacle Mainland !1£1-J.nland South a b 1039(22) 445(12) 280(-) 83(10) 16 51 2 975 425 340 3 1077 4 920 5 872 c Statistics n 5 2 2 1 1 1 X 977 435 310 83 16 51 s 84 90$C.B; 86 a percent common murres in parentheses b dash indicates no estimate of percent of common murres is available c statistical abbreviations:,n=sample size (plots), x=mean, s=standard deviation, C.B.=confidence bound ------ there was white wash indicating more birds had been present, only 150-200 murres were present during the afternoon of July 13. These cliffs had contained nearly 13,000 birds in late June 1980 (Nysewander et al. 1982). Most likely, poor food availability had caused birds to temporarily abandon this colony during 1989. Phenology at Agattu--Like in 1988, the peak of hatch for common murres at Agattu occured the last 2 weeks of July {Fig. 7). In 1989, about 75% of the eggs hatched July 15-26, so the peak of fledging was August 5-16. Phenology at Buldir--Thick-billed murres at Buldir had a similar reproductive schedule to common murres at Agattu. Most eggs hatched July 17-28 {Fig. 7), very similar to the timing of the hatch at Buldir in 1988. Most chicks fledged between August 7-18, similar to phenology recorded at Buldir in 1988 and 1976 {Byrd unpubl. data). Productivity at Agattu--About 71% of the pairs of common murres hatched an egg on plots at Agattu in 1989 {Table 21, Appendix 13). Over 80% of the chicks reached fledging age, so overall, about 57% of the pairs produced fledglings {Table 21). Similarly high chick survival was reported for these plots in 1988 (Byrd and Climo 1988). Productivity at Buldir--Data were collected on the reproductive performance of thick-billed murres on the same 12 42 Common Murre Hatching Dates Agattu Island, Alaska in 1989 Number of Neala 11-14 15-18 19-22 23-25 27-30 31-3 4-7 8-11 12-15 Dates in July and August Thick-billed Murre Hatching Dates Buldir Island, Alaska in 1989 Number of Neala 9-12 13-16 17-20 21-24 25-28 29-1 2-5 6-9 10-13 14-17 Dates in July and August Figure 7. Distr ibution of hatching dates for murres at Aga t tu and Buldir . Islands in 1989 . 43 Table 21. Reproductive performance of common murres at Agattu Is., Alaska in 1989. Measur'es of Success a b c d e Statistics HatchinJL Fled_ging Reproductive Index n 17 17 17 17 X 0.71 0.81 0.57 0.26 s 0.03 0.04 0.04 0. 18 90% C.B. 0.06 0.07 0.08 0. 11 a statistical abbreviations: n=sample size, x=mean, s=standard deviition, C.B.=confidence bound b chicks/active s±te (i.e., one where an egg was layed) c chicks fledged/site where an egg hatched d chicks fledged/active site e number of fledglings per mean number of adults 44 plots at Buldir in 1988 and 1989. We estimated that about 82% of the breeding pairs hatched an egg, and 83% of the chicks survived to fledging (Table 22, Appendix-14). Overall nearly 70% of the nesting pairs produced fledglings, similar to the success recorded for Buldir in 1988 (Table 22). ACKNOWLEDGMENTS We appreciate the efforts of the following Fish and Wildlife Serice personnel who assisted us with field observations: Agattu I., Debbie Groves, Sarah Toadvine, Van Klett, Kemper Carlson, and Adrienne Buck; Buldir I., Mark Hipfnerr Greg Zuberbier; Amukta I., David Blomstrom, Mark Wojcikiewicz, Hugh Knechtel and Andre Nault. Blomstrom and Nault also conducted surveys on Aiktak. 45 . Table 22. Reproductive performance of thick-billed murres at Buldir Is., Alaska in 1988 and 1989. Measures of Success b c d e a Hatching Fledging Reproductive Index Statistics 1988 1989 1988 1989 1988 1989 1988 1989 n 12 12 12 12 12 12 12 12 X 0.80 0.82 0.90 0.83 0.73 0.68 0.52 0.44 s 0. 1 0 0.0~ 0. 11 0.02 0.14 0.02 0. 13 0. 1 0 90% C.B. 0. 17 0.05 0. 15 0.04 0.23 0.04 0.22 0.08 a statistical abbreviations: n=sample size, x=mean, s=standard deviation, C.B.=confidence bound b chicks/active site (i.e., one where an egg was layed) c chicks fledged/site where an egg hatched d chicks fledged/active site e number of fledglings per mean number of adults ltC LITERATURE CITED Bailey, E.P. and J.L. Trapp. 1986 A reconnaissance of breeding marine birds and mammals in the east-central Aleutian Islands--Kasatochi to the Islands of Four Mountains-summer 1982, with notes on other species. Unpub. report U.S. Fish and Wildlife Service, Homer, Alaska. Byrd, G.V. 1978. Birds of Buldir Island, Alaska with notes on abundance and nesting chronology. Unpubl. report. U.s. Fish and Wildlife Service, Adak, Alaska. 132 pp. Byrd, G.V. 1986. Results of seabird monitoring in the Pribilof Islands in 1986. Unpubl. report. u.s. Fish and Wildlife Service, Adak, Alaska. 66 pp. Byrd, G.V. 1989. Seabirds in the Pribilof Islands, Alaska; Trends -and monitoring methods. Ms Thesis. University of Idaho, Moscow. Byrd, G.V. and L.A. Climo. 1988. The status of ledge-nesting seabirds in the western Aleutian Islands, Alaska in summer 1988. Unpubl. report. u.s. Fish and Wildlife Serv., Adak, Alaska Byrd, G.V. and R.H. Day. 1986. The avifauna of Buldir Island, Aleutian Islands, Alaska. Arctic 39:109-118. Day, Robert H., Brian E. Lawhead, Tom J. Early, and Elaine B. Rhode. 19~9. Results of a marine bird and mammal survey of the western Aleutian Islands--Summer 1978. Unpubl. report. U.S. Fish and Wildlife Service, Adak, Alaska. 199 pp. - DeGange, Anthony R. and Richard A. Wood. 1984. Trip report: Buldir Island--June 1984. Unpubl. report. Alaska Field station, Denver Wildlife Research center, U. s . Fish and Wildlife Service, Anchorage, Alaska. 23 pp. Forsell, Douglas J. 1983. Progress report on field studies in the Aleutian Islands, Semidi Islands, and Bering Sea, 1983. Unpubl. report. Alaska Field Station, Denver Wildlife Research Center, u.s. Fish and Wildlife Service, Anchorage, Alaska. 6 pp. Forsell, Douglas J. and Christopher J. Ambroz. 1983. Seabird populations of eastern Agattu Island--Summer 1982. Unpubl. report. U.S. Fish and Wildlife Service, National Fisheries Research Center--Seattle, Migratory Bird Section, Anchorage, Alaska. 17 pp. 47 Hunt, G.L., z. Eppley, B. Burgeson, and R. Squibb. 1981. Reproductive ecology, foods, and foraging areas of seabirds nesting on the Pribilof Islands, 1975-1979. Environ. Assess. Alaskan Cantin. Shelf Final Rep. Prine. Invest. NOAA Environ. Res. Lab., Boulder, Colo. 12:1-258. Nysewander, D., D. Forsell, P. Baird, D. Sheilds, G. Wailer, and J. Kogan. 1982. Marine bird and mammal survey of the eastern Aleutian Islands, summers of 1980-81. Unpubl. report. U.S. Fish and Wildlife Service, Anchorage, Alaska. Springer, A. and G.V. Byrd. 1988. Seabird dependence on walleye pollock in the southeastern Bering Sea. Proceed. Intern. Symposium on the Biology and Management of Walleye Pollock, October 1988, Anchorage, AK. 48 Appendix 1. Reproductive performance of red-faced cormorants on index plots at Agattu Island, Alaska, in 1989. a Statistic~s______ Aga Cove Island Cove 90% Paramet~e~r______~(A~l=l~S~i~t~e~s~) _____~9~/_1~7L/~1~8 ______~1L9~a~ ______Total n X s C.B. total no. of nests 22 22 18 62 no. of nests with > 1 11 19 12 42 chick maximum no. of chicks 26 47 24 97 seen no. of nests where > 1 3 10 4 17 :r chick fledged I-' total no. of fledglings 5 17 4 26 b fledging success 0. 19 0.17 3 0.24 0. 10 0.42 overall c productivity 0. 14 0.45 0.22 3 0.27 0. 16 0.65 a statistical abbreviations: n=sample size, x=mean, s=standard deviation, C.B.=confidence bound b number of fledglings per maximum number of chicks seen c chicks fledged per nest 0.24 0.10 0.42 Appendix 2. Black-legged kittiwake population counts on index plots at Agattu Island, Alaska in 1989. a Statistics Plot n X s 20~ C. B. b 4 8 ( 8) 240.6 (105.0) 53.2 (10.2) 16. 4 ( 1. 2) 5 8 ( 8) 144.6 (54.5) 28.5 ( 5. 1 ) 30.2 ( 5 . 4 ) 6 8 ( 8 ) 131.0 (84.0) 11.9 ( 4. 3) 12.6 ( 4. 5) • 7 8 (8) 170.0 (91.6) 17.5 ( 3. 6) 18.6 ( 3. 9) 14 8 (8) 160.6 (79.5) 24.9 (4.2) 26.4 (4.4) 17 8 (8)- 713.3 (379.5) 56.4 (23.2) 59.8 (24.6) 74 1 1 ( 11) 279.8 (168.5) 29.2 ( 5. 1 ) 24.4 (4.2) 75 1 1 ( 11) 318.0 (190.9) 21.9 ( 4. 6) 18.2 ( 3. 8) 21 11 ( 11) 41.0 ( 4. 0) 19.7 ( 1 • 5) 16.4 ( 1. 2) 22 1 1 ( 11) 438.5 (262.1) 42.6 ( 6 • 9 ) 35.5 ( 5 . 7 ) 25 1 1 ( 1 1 ) 127.5 (68.8) 12.5 (2.4) 10. 4 (2.0) 26 11 ( 1 1 ) 13.8 (9.8) 6.9 (0.9) 5.8 (0.8) a statistical abbreviations: n=sample size, x=mean, s=standard deviation, C.B.:confidence bound b nest counts in parentheses A-2 ------ A-3 ' . Appendix 4. Counts of black-legged kittiwakes in index plots at Main Colony on Arnukta Is., Alaska in 1989. Date Plot 6/30 7/5 7/6 7/7 a A1 0 2 (0) 3 (0) 0 A2 19 .( 0) 21 (0) 2 (0) 16 (0) A3 4 (0) 12 (0) 20 (0) 14 (0) A4 13 (0) 24 (0) 13 (0) 31 (0) A5 20 (0) 21 (0) 22 (1) 37 (0) B 7 (0) 8 (0) 4 (0) 9 (0) Total 63 88 64 107 a nests in parentheses A-4 ---·---·------Appendix 5. Reproductive performance of black-legged kittiwakes on index plots at Agattu Island, Alaska in 1989. Para.!'l.!J!..!!..r 3 H ~ 6 1 j.!)__ 12 13C 1~ 15 20 21 22A 22C 23A 23D 24.\· 25C Total n X total no. of nests 23 43 27 4.11 44 32 27 36 31 27 34 13 35 32 26 33 27 42 576 no. of nests with 2. 1 egg PI 29 7 23 35 27 8 32 25 16 31 5 32 26 13 24 16 30 393 b laying success 0. 61 0.67 0.26 0.52 0.80 0.84 0.30 0.89 0.81 0.59 0.91 0.38 0.91 0.81 0.50 o. 73 18 0.68 0.04 0.08 no. of nests with 2. 1 10 21 4 14 30 22 6 22 18 12 23 23 19 2 20 7 1 4 268 chick c hatching succe.ss 0.71 0.55 0.57 0.39 0.86 0.81 0.22 0.69 0. 72 0.75 0.74 0.20 0.72 0.73 0.15 0.83 0.44 0.47 18 0.68 0.04 0.06 no. of nests \Jhere 2. 1 10 9 0 10 18 1!1 2 18 18 7 20 0 9 11 0 9 0 3 162 chick fledged d fledging success 1. 00 0.43 0 0.71 0.60 0.82 0.33 0.82 1. 00 0.58 0.87 0 0.39 0.58 0 0.45 0 0.21 18 0.60 0.06 0.10 e reproductive success 0.71 0.31 0 0.~3 0.51 0. 67 0.25 0.56 0.72 0.44 0.64 0 0.28 0.42 0 0.38 0 0.10 18 0.41 0.05 0.09 f overall productivity 0.~3 0.21 0 0.23 0.41 0.56 0.07 0.50 0.58 0.26 0.59 0 0.26 0.34 0 0.27 0 0.07 18 0.28 0.05 0.08 ------a statistical abbreviations: n=sample size, x=mean, s=standard deviation, C.B.=confidence bound b nests where an egg wa:~ layed/nest start (one to which vegetation had been added) c chicks/active nest (one where an agg was layed) d fledglings/successful nest (one where an agg hatched) e fledglings/active nest f fledglings/nest etart Appendix 6. ReprodYCtlve performance or black-legged kitLiwake:t on indeX plot. :a at Buld1r laland• J.la:~ka J.n 1969. or nel't:l 19 22 ?3 19 26 11 31 20 21 23 20 1 ~ 13 15 19 26 33 39 29 16 36 30 27 26 s•• no. or nest a wl th l. 1 egg 1l 11 12 1 ~ 13 13 11 10 ,. 13 23 201 1 a y tng SUCCC:tl5 0.21 0.23 o. 35 0.26 o. -2 o. 09 0.35 0.15 0.57 0.61 0. 65 0.93 0 o. 73 o. 32 0.36 o. 15 0.02 o. •a 0.72 0.6~ 0 0.)3 0.11 20 o. 36 0.05 o. 09 no. or nel!its with 0 2 12 10 10 0 0 2 0 l. 1 ch1clc ·~ hatching succe.s3 o. 25 0 0 o. 16 o.n 0.75 o. 66 o. 77 0.17 0 0 0 o. 03 0.11 o. 25 "0 .. 22 0 20 0.32 0. 06 0.13 no. or ne:.t:~: wher-e > 1 0 0 0 2 2 0 0 2 0 0 28 chick fledged fledging sucee.a.:s 0 0 o. 50 1. 00 0.56 o. 75 0.50 0.20 0 0 0 0.22 0.33 20 o ••• o. 08 0.14 reproductive !U.lCCe:,s 0 0 0.09 0.22 0 ~liZ 0.61 o. 38 o. 15 0 0 0 0.09 0.22 0 2lt 0.1 .. 0.05 o.os overilll producti'l'ity 0 0 0.03 0.10 o. 2q 0.39 0.25 0.1. 0 'o 0 0 0.06 0 o. 07 2" 0.05 0.02 o. 03 ------. ~tat! .!!it. leal abbreviations: n:sat:~ple :Ji:r.e. x""mean, ::~~:::standard deviation, c. B. :eonr ldence bo-und b ne5t:t where an •u va• 1a1ed/ne:st :~-tart. (ooe to vhtcb veget.at1oa had been added) e chick~/active I'H~l.'lt {one: where an egg ... layed) d .fledgli ng.!!l ~l.H:::Ce:l:~ful ne~t. {ono 'Where an egg hatehed.) tledallogs/ou:t1Yo ne:Jt. r fledgl.t l.lg:t/ne3t star-t ' . . Appendix 7. Red-legged kittiwake population counts on index plots at Buldir Island, Alaska in 1989. ·a Statistics Plot n X s 90~ C.B. b 5 4 ( 3) 76.6 (37.9) 15.0 ( 4. 9) 17. 8 ( 5. 8) 6 4 ( 3) ·23.3 (12.6) 4. 1 ( 3. 4) 4.8 ( 4. 1 ) 7 4 ( 3) 13.3 ( 7. 3) 4.7 ( 2. 4) 5.5 ( 2 • 8 ) A 4 ( 3) 214.7 (144.3) 64.4 (34.3) 76.5 (40.8) B 4 ( 3) 42.3 (21.1) 12. 0 (8.2) 14.2 ( 9. 8) c 4 ( 3) 48.7 (32.4) 15.5 ( 1 0 • 5 ) 18.5 (12.5) 15 4 ( 3) 139.4 (95.0) 26.8 ( 8. 1 ) 44.6 (13.6) 1 6 4 ( 3) 134.2 (82.6) 23.2 (7.7) 38.9 (13.0) 17 4 (3) 220.8 (124.8) 32.7 (11.0) .,. 54.9 (18.4) 18 4 ( 3) 113. 2 (74.8) 8.8 ( 4. 4) 14.7 ( 7 • 4 ) 1 9 7 ( 3) 94.0 (51.2) 13.3 ( 3. 7) 22.2 ( 6. 1 ) 20 7 (3) 98.0 (72.2) 11 • 1 ( 6. 0) 18.5 (10.1) 21 7 (3) 62.4 (48.8) 3.7 ( 4. 4) 6. 2 (7.4) 22 7 ( 3) 83.4 (56.2) 13.7 ( 6. 7) 23.0 <11.3) 23 7 (3) 90.6 (63.0) 1 0. 0 ( 1. 9) 1 6 . 7 ( 3. 2) 24 7 ( 3) 1.2 ( 0. 8) 1.0 ( 0. 4) 1.6 co.::n a statistical abbreviations: n=sample size, x=mean, s=standard deviation, C.B.=confidence bound b nest counts in parentheses A-7 Appendix 8. Reproductive performance of red-legged kittiwakes on index plots at Buldir Island, Alaska in 1989. ------a ------~K~i~t~tiwake Lane Plot Di-"'------____ s t a t.£;3 t-=ic.::c:;.;:s,__ ___--:-_ b 90~ Par am~ t e..:..r______,1 -2 .1:-_4 _ _2-6 _..7______;o_8 ___~_31.L_ D-=i...._p__ .:=-T-=o tal._~n,__--'x"---=s. _____:::c:..::.. B. total no. 20 28 36 31 37 14 38 29 233 of nests no. of nests with > 1 egg 4 11 20 22 7 14 8 93 c laying success 0.20 0.04 0.47 0.64 0.59 0.50 0.37 0.27 8' 0.40 0.07 0. 13 no. of nests with 0 0 8 15 6 2 46 > 1 chick d hatching success 0 0 0.47 0.75 0.64 0.86 0.07 0.25 8 0.49 0.11 0.20 no. of nests where 2 1 0 0 4 7 10 0 1 23 chick fledged f' e co fledgling success 0 0 0.50 0.47 0.71 0.17 0 0.50 8 0.50 0.08 0.16 f reproductive success 0 0 0.24 0.35 0.45 0.14 0 0.12 8 0.25 0.07 0. 13 overall g productivi.~t~y______~o~---~o __~o.~·~1~1-~0~·~2~2--~0~·~2~7~~o~·~0~7L-~o __~o~·~0~3,______8~-~o~.~1~0 ____ ~o~·~o~4~--o~·=o=8 a statistical abbreviations: n=sample size, x=mean, s=standard dev~ation, C.B.=confidence bound b includes scattered red-legged kittiwake nests on plots 33, 34C, 39A, 40, 42, 43A, 43B c nests where an egg was layed/nest start (one to which vegetation had been added) d chicks/active nest (one where an egg was layed) e fledglings/successful nest (one where an egg hatched) f fledglings/active nest g fledglings/nest start l ' • Appendix 9. Common murre population counts on index plots at Agattu Island 1 Alaska in 1989. a Statistics Plot n X s 90% C.B. Min. Max. 4 8 47.1 13.0 8.9 32 63 8 8 373.1 28.2 19.3 320 418 9 8 357.9 25.8 17.7 328 396 11 8 437.8 66.7 45.7 349 536 13 8 316.9 39.3 27.0 251 362 74 11- 168.0 13.0 7.1 158 188 75 11 68.6 9.2 5.1 55 82 21 11 6.7 2.4 1.3 4 12 22 11 33.1 4.0 2.2 26 38 25 11 293.4 27.4 14.9 240 328 26 11 524.0 27.7 15.2 486 570 27a 10 163.4 13.7 9.4 140 180 27c 10 50.2 3.5 2.4 44 54 27d 10 315.0 32.6 22.3 260 369 a statistical abbreviations: n=sample size, x=mean, s=standard deviation, C.B.=confidence bound, min.=minimum count, max.=maximum count A-9 ' ' . Appendix 10. Thick-billed murre population counts on index plots at Agattu Island, Alaska in 1989. a statistics Plot n X s 90% C.B. Range 74 11 66.2 10.6 8.8 45-84 75 11 12.6 2.8 2.3 9-18 21 11 15.1 5.2 4.4 9-23 22 11 7.0 3.2 2.7 1-12 25 11 11.7 3.0 2.5 7-15 26 J.1 38.9 6.8 5.7 29-56 27 10 84.6 11.5 10.2 63-98. 28 3 472.3 15.1 60.6 452-488 a statistical abbreviations: n=sample size, x=mean, s=standard deviation, C.B.=confidence bound A-10 Appendix 11. Thick-billed murre population counts on index plots at Buldir Island, Alaska in 1989. a statistics Plot n X s 90% C. B. Range 2 6 24.8 3.6 5.0 21-31 3 6 46.2 4.4 6. 0 41-54 4 6 3. 8 4.0 5.5 0-10 5 6 74.3 21.0 28.9 49-105 6 0 7 0 b A 6 401.5(1.0) 25.1(1.2) 34.4(1.2) 370-438 (0-3) B, 6 330.0(2.8) 44.2(4.3) 60.9(5.0) 254-394 (0-9) c 6 321.7 35.6 48.9 275-370 8 6 182.2 17.5 24.0 151-203 9 6 63.3 5. 6 7.7 57-71 10 6 86.8 8.4 11. 5 75-102 11 6 77.7 4.5 6.2 71-84 12 6 417.5 20.4(2.3) 28.0(2.2) 392-451 (2-8) 13 6 152.2 9.1(1.9) 12.5(1.8) 140-170 (8-13) 14 6 77.0 3. 1 4.3 73-83 15 5 70.2 5. 0 8.3 65-78 16 5 166.8 20. 1 33.6 134-197 17 5 124.8 13. 1 21.8 108-144 1 8 5 67.2 13.7 22.8 48-86 a statistical abbreviations: n=sample size, x=mean, s=standard deviation, C.B.=confidence bound b common murre counts in parentheses A-ll Appendix 12. Counts of murres on plots at 11 Main Colony" Amukta Is., Alaska June 28-July 7, 1989 (all counts made between 1200h-1630h). Date Plot 06/28 06/30 07/02 07/03 07/05 a A1 85 82 (0.16) 75 77 76 (18) A2 135 154 (13) 165 150 148 (18) A3 246 236 ( 3 6) 262 228 244 ( 36) A4 347 320 345 273 236 A5 104 86 104 95 78 B 9.7 77 104 77 70 c 25 20 22 20 20 Total 1039 975 1077 920 872 b Statistics n 5 X 976.6 s 83.9 90%C.B. 86.2 a % commom murres in parentheses b statistical abreviations: n=sample size, x=mean, s=standard deviation, C.B.=confidence bound A-12 ------.. Appendl't. 1). Re"pt'oduollve perrorl!'!iance or C()t:'lQUh uurras on 11\dQl plots at •s•tt.u l:Jland• ------a --· ~•&.!_fJt!-.! ______- _-l:J.J?t e-·l.sland -- Co Yo ------.;u.!'.L!!!H.!'.!'______f!.J'!'!'J'~!I_____ l.j_B__ 2J.L_ll.L....._?.iJ!.._~~!I--.?6C 2I 28.1. _.3,9 __~8 2 lib 11 , ___Jj_b __ ! J.!L....__.!.ld T.!>YL II X a ___..__5/.QJS_,_!..._ • no. of blrdo 85 u 70 25 ., 85 23 63 56 56 !06 "1 6o H9 100 106 1261 preaeot •o no. or a1t.oa with .?. 56 26 lS H 55 !6 32 26 8 16 10 )8 21 17 7 \0 -5 I l •.n: " PO. or t!ltea witb Chick \5 n l3 9 27 38 23 21 2 12 s 20 IS 12 2 29 321 b " hatch in& aucce•• 0.80 o.s• 0.9, o.n 0.79 0.69 0.88 0.72 0.8! 0.25 O.T!> 0.50 0.52 O.Tl 0.70 0.28 0.72 IT o.n 0.03 0.06 no. or &!tea where I cblck )8 13 30 II 26 30 12 20 19 .II 19 6 1 IT 259 rledc.ed ' " 0 tlodsiDg .succeaa 0.8. 0.93 0.91 0.89 0.96 0.79 0.86 0.117 0.90 0.50 o.n 0.80 0.95 o.n 0.50 o.so 0.59 11 O.IU o.ot 0.07 d reproduc:t1•• oueee.sa.. 0.68 0.50 0.86 0.57 0.76 o• 0.15 0.62 0.73 0.12 0.25 0.\0 0.50 0.52 0.35 o.n 0.\2 .lT 0.57 o.o• o.os o••rall produet1¥1ty 0.47 0.28 o.H 0.32 o.S3 0.35 0.52 0.33 a·. 'II 0.12 0.07 0.07 0.13 0.18 o.o• 0.01 0.16 IT 0.26 0.18 o.u a .statlaltcal abbre¥1ationa: Q;sa~ple &it•• xsaean. &satandard deYJ&tJon• C.B.:conCJdonce bo~ad b chlcks/acttYe nc•l a1t• (one wbere a~ &&£ vaa la7ed) c i> dcbteke fled&ed/sueooaarul naat &lle (one vb•r• aQ e&& batcb•d) w.~ Cblcka rledged/•etiYe DeAl 5Jle murre a on ex p ots at Buldir Island, Alaska in 1989. # a .. Statistics ~ 9~1: Parameter ,31A 31B ,31C 32 ,34A J4B 36 ,38A ,38B 32B 32C 4JC Total n X s G.B. b X no. of I I birds 4 1 33 30 82 55 43 21 76 50 24 36 54 545 ~ present no. of sites with > 17 16 1 9 41 34 31 15 47 36 20 22 31 329 1 egg no. of sites with chick 13 14 16 33 24 26 8 42 33 18 17 25 269 c hatching success 0.76 0.88 0.84 0.80 0.70 0.84 0.53 0.89 0.92 0.90 0. 77 0.81 12 0.82 0.03 0.05 no. of sites where chick 1 1 13 13 25 24 22 6 35 26 15 13 21 224 fledged d > fledging success 0.85 0.93 0.81 0.76 1.00 0.85 0.75 0.83 0.79 0.83 0.76 0.84 12 0.83 0.02 0.04 ..l e =reproductive success 0.65 0.81 0.68 0.61 0.70 0.71 0.40 0.74 0.72 0.75 0.59 0.68 12 0.68 0.02 O.OlJ r overall productivity 0.34 O.lJ5 0.45 0.32 O.lJ5 0.53 0. 33 0. 4 g., 0.54 0.67 0.36 0.39 12 0.41J 0.10 0.08 5tatistical abbreviations: n=sample size, x=mean, s=standard deviation, C.B.=confidence bound b based on five counts in July 1989 c chicks/active nest site (one where an egg was layed) d chicks fledged/successful nest site (one where an egg hatched) e chicks fledged/active nest site f number of fledglings per mean number of adults