LITTORAL ZONE USE BY POST~BREEDING SHOREBIRDS ON THE COLVILLE RIVER DELTA, :

-- PROGRESS REPORT -­ FISCAL YEAR 1987

Brad Andres Ohio Cooperative Fish and Wildlife Research Unit 1735 Neil Avenue Ohio State University Columbus, OH 43210

prepared for U.S. Fish and Wildlife Service Alaska Investigations Branch of Wetlands and Marine Ecology lUll East Tudor Road Anchorage, AK 99503

May 1988

This study is supported through a Research Work Order between the U.S. Fish and Wildlife Service and Ohio State University. LITTORAL ZONE USE Page 2

INTRODUCTION

In 1986, the U.S. Fish and Wildlife Service, through the North Slope Bird-Habitat Study, charged the Ohio Cooperative Fish and Wildlife Research Unit with the task of assessing post-breeding shorebird occurrence in the littoral areas of the Colville River delta. This assignment complemented the Study's larger survey of bird and habitat relationsnips on the Alaskan central coastal plain (see Field et al. in prep.}. ~rough a Research Work Order between the Service and the Unit, a study was begun in 1986 to survey littoral habitats for presence of post-breeding shorebirds. The research is also the basis for a r·1aster's thesis. This report presents results of work conducted during 1987.

BACKGROUND

Shorebirds are long distance migrants, traveling from boreal or breeding grounds to tropical or southern hemisphere wintering grounds. Recent studies of staging and migrating shorebirds (Charadrii} have docuwented abundance and habitat use in temperate regions (e.g., Pitelka 1979}. These investigations determined areas where shorebirds \'lere particularly abundant during staging and migratory phases of their life cycle. Although dispersed during the breeding season, many shorebirds concentrate in small, usually estuarine areas during migration (rlyers 1~83). Areas that occasionally host over a willian shorebirds during staging have been found throughout the world (United Kingdom: Prater 1~81; North American Atlantic coast: r·lorrison and Harrington 1979, Hicklin 1987; Pacific coast: Senner and Howe 1984}.

Within arctic Alaska, Connors et al. (1979) shoHed that shorebirds move oy mid summer from breeding areas to littoral habitats which are characterized by periodic saltwater inundation. The move to littoral LITTORAL ZONE USE Page 3 habitats may be related to changes in prey availability (Connors et al. 1979). Changes in habitat use are also associated with an increase in shorebird density and diversity as they arrive in littoral habitats. Use of the littoral zone by shorebirds in arctic Alaska has been documented from the Chukchi Sea and coasts in a series of surveys from 1975-1981 sponsored by the Outer Continental Shelf Environmental Assessment Program (Connors and Risebrough 1976, 1977, 1978, 1979, l98u, Connors and Connors 1985, Connors et al. 1984). Surveys of shoreline habitats on the eastern North Slope were conducted by f,loitoret (1983) and the Arctic National Wildlife Refuge (Garner and Reyno 1ds 1986) •

The Colville River delta provides the most extensive salt marshes and terminal silt barrens along the central Beaufort coast, and these areas are expected to support large numbers of staging shorebirds (Connors et al. 1981). Surveys of staging shorebirds conducted on nearby Fish Creek area have demonstrated substantial use by shorebirds (Connors et al. 1984). Although bird surveys have been conducted in the past on the Colville River delta, no information has been gathered on littoral habitat use by post-breeding shorebirds. During a pilot study in sur.1mer 1986, I determined that substantial numbers of shorebirds were occurring in tne littoral zone of the delta, outside the bounds of the Study 1 S regular survey plots (Andres et al. 1987).

OBJECTIVES

The objectives of this study are:

1. To determine the abundance of post-breeding shorebirds using the littoral areas of the Colville River delta; LITTORAL ZONE USE Page 4

2. To determine if post-breeding shorebirds occur in different abundances in the habitats found in the littoral zone;

3. To develop methods for assessing turnover rates of post-breeding shorebirds occurring in the delta; and

4, To cnaracterize the behavior of shorebirds present in the littoral areas of the delta.

~IETHODS

STUDY AREA

The Colville River delta lies about 75 km west of Prudhoe Bay. The river, draining 29% of the North Sl~pe, forms a'600 km2 delta where it empties into Harrison Bay (Walker 1983). The littoral .zone extends approximately 6 km inland from the bay (Figure 1}.

SAHPLING DESIGN

Vegetation studies by Marken (Rothe et al. l982lt Walker et al.(l980), and North Slope Study personnel were used as a basis for distinguishing five habitat types (Table 1): terminal shoreline silt barren, subterminal shoreline silt barren, interior silt barren, halophytic herb barren, and saline grass/sedge tundra. The latter two habitats are defined as coastal wetlands (VIII) by Bergman et al. (1977). One additional non-littoral habitat, channel silt barren, was sampled. Table 1 provides a brief description of the habitats and their relationship to Hork by Harken {Rothe et al. 1982) and \Jalker et a 1. { 1980). LITTORAL ZONE USE Page 5

A vegetation covermap, derived by rlarkon (Rothe et a 1. 1982) and consisting of five habitat types, was divided into 65 strata. Location of these strata were identified by sections (Figure 1, Appendix 1). An example of the locations of these types is shown in Figure 2.

The strata, each consisting of a single habitat type, varied in size. The sampling frequency depended on accessibility and expected variation in bird densities. This study design follows Cochran's (1977:96-99) "optimal allocation with stratified random sampling".

The size, location by section (see Figure 1), and number of surveys for each stratum are presented by habitat in Appendix 1. Ground-truthing of the covermap occurred prior to and during the first week of surveys. Less than 3% of the littoral area of the delta was excluded from sampling due to constraints in time and access. Recause vegetational composition of these areas could not be verified, they are not included in the analysis. Thus, estimates of total numbers of shorebirds are conservative. Areas and lengths of plots were determined using the digitizing software package SigmaScanR at Ohio State University. Area measurements entailed the land portion only, excluding Hater bodies evident in cover maps at 1:30,000. Shorelines were measured in terms of length and area. Area determinations of shoreline and channel strata were dictated by the depth of shorebird use from the water interface. Widths of shoreline and channel plots varied from 5 to 50 meters.

SAHPLING PROCEDURES

The visitation schedule for each stratum was planned at the start of the season and changed only as a result of severe weather or logistic problems. On each day that a stratum was sampled, observers covered the entire stratum unless bad weather prevented complete coverage. LITTORAL ZONE USE Page 6

Plots were surveyed by a two-person crew. During each survey, numbers of individuals and species on each habitat plot were recorded. Direction of birds flying over the plot during a survey were recorded in degrees when possible. The following behaviors were recorded: feeding (probing or pecking), sleeping, preening, \valking, swimming, breeding [courtship or nest defense calls), standing, and flushed. Microsite information collected on individuals consisted of location, substrate, and moisture r.1easures. Location measures 11ere recorded as pond basin, pond/lake edge, or land. Substrate categories included: barren ((15% cover), sparsely vegetated (15-75% cover), or well vegetated (>75% cover). The four moisture measures used 1vere moist, film, water level between a bird 1 S digits and the distal end of the tibiotarsus, water level above the distal end of the tibiotarsus. Analysis has not yet been completed on the microsite information.

Two to four stationary point-counts, each lasting 30 ninutes, were conducted at locations along channels on each survey-day. During the point count species, number, direction, and whether or not the bird landed were recorded. For each point-count weather information was collected. For analysis of migratory direction, headings were grouped into four directions: north (315°-44°), east (45°-134°), south (135°-224°), and Hest (225°-314°). Analysis of point-count data is continuing.

ANALYSIS

Statistical analysis was carried out using standard formulae for stratified rando~1 sampling (Cochran 1977). Means, totals, and variances were calculated within strata and then combined appropriately to obtain estimates for all or part of the delta. In analysis of temporal trends, means for each week were needed. However, since individual strata were sampled at most once a week, variances could not be calculated for the individual strata. Therefore, strata with the same habitat type 11ere ''

LITTORAL ZONE USE Page 7 co~bined to create super strata, each of which had more than one survey within the period of interest (see Cochran, 1977, pp. 136-138 for additional explanation). The usual formulae for stratified random sampling were then applied to the results for these super strata.

RESULTS AND DISCUSSION

ABUNDANCE AND HABITAT USE

Bet\leen July 11 to September 2, 46 survey-days resulted in over 650 observer-hours. Seventeen species of shorebirds were recorded during the surveys. Two additional species, Wilson's phalarope (photo obtained) and sharp-tailed sandpiper, were observed in littoral habitats prior to survey initiation. Five of these species comprised 90% of the signtings (Table 2).

Since so few birds were observed on channel silt barrens, despite surveying 115 km of channel barrens, and because this habitat type is non-littoral, it was excluded from further consideration. Also, interior silt barrens received no use and are not considered in habitat calculations (use on terminal silt barrens will be discussed later).

Mean densities, total numbers, and their associated standard errors were calculated for species providing >1% of the observations over the entire study period. Appendix 2 presents these calculations for each species by habitat type. Table 3 shows the estimated abundances of shorebird species across all habitats. Co~paring total nu~bers for all species between habitats, reveals that dunlin are by far the ~ost abundant post-breeding shorebird in the delta. nunlin are more abundant than all other species combined. LITTORAL ZONE USE Page 8 differential habitat use was determined by estimating proportions of total numbers for each species in each habitat type Appendix 3. Use of shorelines is clearly dominated by dunlin. With almost all species there is a clear dichotomy-between shoreline and saltmarsh use. Excluding dunlin, all other species show a preference for saltmarsh habitats and follow a similar pattern (Table 4). None of the species showed habitat preferences that differed significantly from the means when dunlin were excluded. It appears, however, that differential use of saltmarsh habitat types does occur but is masked by considering average values over the entire summer. Future analysis will be directed toward assessing habitat preferences thoughout the season.

Use on terminal silt barrens by dunlin is restricted to a narrow shoreline band along the ocean interface. The interior bulk of these extensive barrens dries out as summer progresses and is unattractive to foraging shorebirds. Although the entire terminal silt barrens comprise 41.32 km 2 of the delta, only 7% of this area is used by shorebirds.

Distribution of shorebirds along the shoreline is far from uniform. Table 5 presents totals by section of the delta. Even within a section, concentrations of birds exist (Figure 3), perhaps due to the distribution of intertidal invertebrates. The presence of invertebrates appears to be related to the slope of the shoreline and the protection from wave action that it provides. More detailed studies of the shorelines are planned for the upcoming field season. snorebird use of vegetated saltmarshes is characterized by shorebirds foraging within shallow pond basins. The majority of observations made during the second 4 weeks of the study period were of birds occurring in pond basins (Figure 4). Shorebird foraging strategies in pond basins consisted of water-surface feeding by phalaropes and benthic probing by dowitchers, stilt and western sandpipers, and dunlin. Phalaropes comprised 32% of the pond basin sightings. Late in the season, sediments of coastal ponds ~ay offer more prey than the surrounding LITTORAL ZONE USE Page 9

tundra (Connors et al. 1979). Hence, pond depth may be an important .component in assessing littoral zone habitat use.

Preliminary evidence, also collected during the latter four weeks of the study period, indicates that differences in densities of shorebirds may exist between distinguishable cover types within the saline grass/sedge tundra habitat (Table 6). Differences in use of halophytic herb patches seems to be dependent on the moisture level of the patch. Table 7 presents a comparison of average densities of shorebirds for dry strata and moist strata in two sections. All these preliuinary results will be pursued in the forthcoming field season.

TEMPORAL TRENDS IN ABUNDANCE

Weekly &Ean densities and total numbers were calculated for all identified species providing >1% of the observations. Totals and standard errors are given in Appendix 4. Overall species numbers peaked between August 9 and August 20 (Figure 5). This peak corresponded with a peak occurring on the shoreline habitats and was primarily caused by influxes of dunlins. Salt marsh habitats received peak use a week later (August 15 -August 30). However, peaks for individual species deviated from this pattern. High use of saltmarshes early in the season reflects certain species preferences for these habitats and the occasional use by peripheral breeding species (Fiqure 6). Distribution of species totals through time is shown for each species in Appendix 5.

Generally, maximum nu1~bers in each habitat parallelled the overall peak for individual species. Several exceptions to this pattern follow. Proportions of dunlin observed in saltmarshes greatly increased during the later weeks. Initially high proportions of dunlin observed in saltmarshes (but s1nall numbers) detected early in the season were due to forays by local breeders. Ruddy turnstones also nested in or near saltmarshes and displayed early season peaks. A second peak of LITTORAL ZONE USE Page 10 turnstones in week 5 was caused by migrants occurring on the shorelines (Figure 7). Baird 1 S sandpiper and both plovers peaked during the second week exclusively in saltmarshes and were subsequently observed ~ore proportionately in all habitats. The nature of the bimodality found in the red-necked phal~rope distribution remains unclear.

ACTIVITY OF SHOREBIRDS

Feeding was the do111inant activity of shorebirds observed in the delta. This was true for all species although, the prevalence of foraging behavior of an individual species varied from 57-89% of the observations (Appendix 6). Distribution of activity is determined from the total of classified observations. Not all individuals were able to be behaviorally classified. Numbers of undetermined individuals of each species is also given in Appendix 6. Foraging behavior dominated the activity tif shorebirds in all habitats. A somewhat greater proportion of birds were noted feeding on shorelines than in saltmarshes (Figure 8).

Only one large flock of birds (250) was observed sleeping on a subterminal shoreline (accounting for the higher incidence of sleeping in this habitat type). This flock was observed nestled down amidst the driftwood strand. Similar occurrences of individual birds resting in the driftwood strand \vere noted throughout the sumr;1er. THenty-four hour observations made earlier in the season indicate that shorebird flocks forage round-the-clock during continuous daylight. Less than 10% of the birds observed were found sleeping in any hour. It appears that sleeping is a rare activity of shorebirds during time on the delta. Pernaps birds are concentrating more on feeding in the littoral areas of the delta and then moving more inland to roost. Preening was also a rare behavior and may be associated with arrival on the delta. In one instance a flock of 37 red phalaropes was observed landing on a shoreline and immediately began preening. LITTORAL ZONE USE Page 11

DIRECTIONAL MOVEMENT OF SHOREBIRDS

For analysis of migratory direction, headings were grouped into four directions: north (315°-44°), east (45°-134°), south (135°-224°), and west (225°-314°). The dominant direction of rdigrating shorebirds passing through the delta appears to east. Only two species, dunlin and western sandpiper, were primarily seen heading to the west. Proportions of individuals heading in four r1ajor directions for each species are presented in Table 8. All species with the exception of stilt sandpipers showed a prominent migration direction.

SUMMARY

Individual plot counts along shorelines produced more than 200 birds/kn during migratory peaks. Similarly, plot counts in saltmarsh habitats produced above 700 birds/km2 during migratory peaks. These values exceed maxi~um shoreline counts of 100 birds/km at Barrow and maximum densities of 600 birds/km2 at Fish Creek (Connors 1984). However, average values in Connors' study were not given. Direct comparison of the Colville 1 s aoundances with other North Slope sites is difficult because of the lack of variance measures ~lith reported means and differences in habitat measurements. Further comparisons of this study's results with other North Slope studies is currently underway.

Timing of peak migration for dominant species corresponded with patterns found at Barrow, although species composition differs srn1ewhat {Connors et al. 1979). Dominant species at Barrow are linked to the presence of gravel shorelines. The most intensive use in the littoral zone in the Colville River delta occurs on the tenninal silt barren shorelines. Although this area occupies only 3% of the littoral area of the delta, it receives 44% of total shorebird use (Table 9). The shorebird assemblage on the shorelines is clearly dominated by a "mudflat'' LITTORAL ZONE USE Page 12 species, the dunlin. Connors et al. (1979) listed the dunlin as being only moderately susceptible to littoral zone disturbances at Barrow. At Barrow, dunlin do not always make the dramatic shift to the littoral zone that is observed in other species (Holmes 1966). ~e dependence of dunlin on the terminal snorelines of the Colville River delta, illustrated by large numbers and preponderance of feeding activity, make tne species highly susceptible to oil-related accidents that would impact shorelines.

Summary of the ecology of post-breeding shorebirds using the littoral zone is given in Table 9. The table shows doninant habitat used (either shorelines, halophytic herb, saline grass/sedge, or the latter two co~bined as Saltmarsh) estimated mean density in the preferred habitat (birds/km2), peak of migration, total for all habitats during the peak week, and direction of migration.

PLANS FOR SUMMER AND FALL, 1988

A two-person crew will be on the Colville River delta during the 1988 field season. Goals of the suRner work are:

1. To continue delta-wide littoral zone surveys with current habitat strata at a reduced rate to compare yearly variation;

2. To concentrate on detecting ptloto-interpretable differences that occur within major habitat types to refine estimates of shorebird habitat use;

3. To refine point count method to get an accurate estimate of turnover rate of delta shorebird species; and LITTORAL ZONE USE Page 13

4. To concentrate on observing birds for longer periods in order to determine age effects on behavior and patterns habitat use.

During the fall, data will be entered into the computer and analyzed. Final reports and the thesis will be completed in the winter. LITTORAL ZONE USE Page 14

LITERATURE CITED

Andres, B., ~1. Woodrey, and J. Bart. 1987. Shorebird use of littoral zone habitats in the Colville River delta. In Bird-Habitat associations on the North Slope , Alaska - 1986 Progress Report. U.S. Fish and ~ildl. Serv., Alaska Investigations -Wetlands and Marine Ecology. Anchorage, AK.

Bergman, R.D., R.L. Howard, K.F. Abraham and M.W. Weller. 1977. Waterbirds and their wetland resources in relation to oil development at Storkersen Point, Alaska. U.S. Fish and ~ildl. Serv., Resource Publication 129. 39 pp.

Cochran, H.G. 1977. Sampling Techniques. Third Ed. John ~Jiley & Sons. New York, NY. 428 pp.

Connors, P.G. 1984. Regional patterns in coastal shorebird communities of arctic and subarctic Alaska. Annual Reports of Principal Investigators. BLM/NOAA, OCSEAP. Anchorage, AK. pp. 59-95.

Connors, P.G. and R.W. Risebrough. 1976. Shorebird dependence on arctic littoral habitats. Annual Reports of Principal Investigators. BLM/NOAA, OCSEAP. Boulder, CO. 55 pp.

Connors, P.G. and R.W. Risebrough. 1977. Shorebird dependence on arctic littoral habitats. Annual Reports of Principal Investioators. BLM/NOAA, OCSEAP. Boulder, CO. 121 pp.

Connors, P.G. and R.~J. Risebrough. 1~78. Shorebird dependence on arctic littoral habitats. Annual Reports of Principal Investigators. BLM/NOAA, OCSEAP. Boulder, CO. 81 pp. LITTORAL ZONE USE Page 15

Connors, P.G. and R.W. Kisebrough. 1979. Shorebird dependence on arctic littoral habitats. Annual xeports of Principal Investigators. BLM/NOAA, OCSEAP. Boulder, CO. 59 pp.

Connors, P.G. and R.W. Risebrough. 1980. Shorebird dependence on arctic littoral habitats. Annual Reports of Principal Investigators. BLM/NOAA, OCSEAP. Boulder, CO. 16 pp.

Connors, P.G. and C.S. Connors. 1985. Shorebird littoral zone ecology of the southern Chukchi coast of Alaska. Annual Reports of Principal Investigators. BU1/NOAA, OCSEAP. Anchorage, AK. 35:1-57.

Connors, P.G., J.P. f-lyers, and F.A. Pitelka. 1979. Seasonal habitat by Alaskan arctic shorebirds. Studies in Avian Biology 2:101-111.

Connors, P.G., S.R. Johnson, and G.J. Divoky. 1981. Ecological characterization of the Sale 71 environr,1ent - Birds. In Beaufort Sea-Sale 71-Synthesis Report. BLIVNOAA, OCSEAP. Juneau, AK. pp. 39-42.

Connors, P.G., C.S~ Connors and K.G. Smith. 1984. Shorebird littoral zone ecology of the AlasKan Beaufort coast. Annual Reports of Principal Investigators. BLM/NOAA, OCSEAP. Anchorage, AK. 23:295-396.

Field, R., F. Gerhardt, J. Tande, G. Balogh, R. MacAvinchey, J. Bart. (in prep.) Bird-habitat associations on the North Slope, Alaska, Progress Report, Fiscal Year 1987. U.S. Fish and Wi1dl. Serv., Anchorage, AK.

Garner, G.W. and P.E. Reynolds. 1986. Baseline study of the fish, ¥1ildlife, and their habitats. Final Report, Arctic National 1,~ildlife Refuge Coastal Plain Resource Assessment- Volur1e 1. U.S. Fish and Wildl. Serv. Anchorage, AK. 392 pp. LITTORAL ZONE USE Paqe 16

Hicklin, P.W. 1987. The migration of shorebirds in the Bay of Fundy. Wilson Bulletin 99(4):540-570.

Holmes, R. T. 1966. Breeding ecology and annual cycle adaptations of the red-backed sandpiper (Calidris alpina) in Northern Alaska. Condor 68:3-46.

Morrison, R.I.G. and B.A. Harrington. 1979. Critical shorebird resources in James Bay and eastern . Transactions of the Forty-Fourth North American Wildl. Conf. pp. 409-577.

Moitoret, C.S. 1983. Bird use of Arctic coastal snorelines at Canning River delta, Alaska. f,1S Thesis. University of Alaska. Fairbanks, AK. 63 pp.

Myers, J.P., 1983. Conservation of migrating shorebirds: Staging areas, geographic bottlenecks, and regional r.1ovements. Ai1er. Birds 37:23-25.

Pitelka, F.A. 1979. (ed.) Shorebirds in 1:1arine environments. Studies in Avian Biology No. 2. Cooper Ornithological Society. 261 pp.

Prater, A.J. 1981. Estuary birds of Britain and Ireland. British Trust for Ornithology. Calton, UK. 440 pp.

Rotne, T.C., C.J. Markon, and L.L. Hawkins. 1982. 1/aterbird populations and habitats in the Colville River delta, Alaska. Unpubl. Rep. U.S. Fish and ~Jildl. Serv., Special Studies. Anchorage, AK.

Senner, S.E. and ~I.A. Howe. 1984, Conservation of r!earctic shorebirds. Behav. of Marine Organisms 5:379-421.

\Jalker, D.A., K.R. Everett, P.J. Weber and J. Brmm. 1980. Geobotanical Atlas of tne Prudhoe Bay region, Alaska. CRREL Report 80-14. U.S. Army Corps of Engineers. hanover, tlH. ti9 pp. LITTORAL ZONE USE Pa~e 17

Walker, H.J. 1983. Guidebook to permafrost and related features of the Colville River delta, Alaska. Guidebook 2. Alaska Division of Geological and Geophysical Surveys, Anchorage, AK 99503. 34 pp. Figure 1. Inland extent of the littoral zone of the Colville River delta and six delineated sections (see text for section explantion, K = Kupigruak Camp location). Figure '· Location of littoral habitat types found on the Colville River delta (A = Terminal Shoreline Silt Barren, B = Subterminal Shoreline Silt Barren, C = Interior Terminal Silt Barren, D = Channel Silt Barren, E = Halophytic· Herb Barren, F = Saline Grass/Sedge Tundra, shaded= water). Figure 3. Distribution of shorebirds along the terminal shoreline silt barren of section 2 on August 17. Figure 4. Proportion of shorebird observations recorded in pond basin, pond edge and land locations in saline grass/sedge tundra during the second four weeks.

U1 1.0 z 0 0.9 ~ 0.8 >a::: w 0.7 U1 OJ 0 0.6 lL.. 0 0.5 (/) 0.4 z 0 0.3 li: 0 0.2 a. 0 0.1 a::: a. 0.0 POND POND LAND BASIN EDGE Figure 5. Temporal changes in total numbers of shorebirds in littoral habitats of the Colville River delta.

6~ 6000 5~ 5000 en a: w ·~4000 CD :I ::> 3500 z .)()()() ~ 1- 2~ 0 1- 2000 1500 1000 ~ 0 13 21 215 4 11 18 26 1 JULY AUCUST SEPT. Figure 6. Temporal changes in habitat use {proportions of total numbers} in the littoral zone of the Colville River delta.

'l"ERWIHAI.. SHOREUHE - SUB't'ERWINAL sHoRE:uN£ IZ2J St.UNE GRASS/SEDCE a J500 HA1...0PHY11C HERS c:1 J150 . en 2800 a: w OJ 2450 :::E ::;) z 2100 - _J 1750 ~ 0 1400 1- 1050 700 - 350 I~ 0 B I I I~ I~ 13 21 28 4 11 18 26 1 JULY AUGUST SEPT. Figure 7. Temporal changes in total numbers of ruddy turnstones in saltmarsh and silt barren habitats.

SHORELJNES SAL.Tt.CARSHES ·-· 55 ·-· 50 45 40 tf.l 0::: LIJ J5 a:l :I JO ~ z 25 ~ • g 20 15 10 5 /·~ \ 0 13 21 28 ... 11 18 28 1 JULY AUGUST SEPT. Figure 8. Activity of shorebirds (proportions of observations) recorded in the littoral habitats of the Colville River delta.

1.0 TERt.fiNAI.. SHOREUNE SUSTERt.AINAI.. SHOREUNE IZ2J 0.9 -a f/) SAUNE GRASS,ISEDG£ z 0 o.a HALOPHYnC HERB CJ ~ 0.7 ~ l.rJ mf/) 0.6 0 "'- 0.5 0 z 0.4 0 § 0.3 0 0.. 0 0.2 a:: Q. 0.1 0.0 FEED STANO SLEEP Table 1. Brief description of littoral habitats used as sampling strata.

~lARK ON DOMINANT WALKER HABITAT TYPE CODES VEGETATION CODES

Terminal Shoreline 16 none Barren (VII) Silt Barren

Subterminal Shoreline 16 none Barren (VI I) Silt Barren

Interior Silt Barren 16 none Barren (VI I)

Channel Silt 16 none Barren (VI I) Barren Halophytic Herb 08 sparse;Dupontia, Sparse (VI) Barren 85 Ste 11 er i a, Car ex saline? Saline Grass/Sedge 06,65 Puccinellia,Carex, Wet sedge tundra 07,75 Eriophorum tundra)saline areas (I Ia) Table 2. Number of shorebird sightings in littoral areas of the Colville River delta, 1987.

SPECIES CODE Nut1BER PERCENT Dun lin DUN[ 10249 65.2 Semipalmated Sandpiper SESA 1870 1.9 Western Sandpiper WESA 1028 6.5 Red)necked Phalarope RNPH 920 5.9 Pectoral Sandpiper PESA 351 2.2 Stilt Sand pi per STSA 242 1.6 Red Phalarope REPH 205 1.3 Black-bellied Plover BBPL 203 1.3 Ruddy Turnstone RUTU 167 1.1 Lesser Golden Plover LGPL 137 0.9 Long)billed Dowitcher LBDO 115 0.7 Baird's Sandpiper BASA 44 0.3 Sanderling SAND 25 0.2 Buff)breasted Sandpiper BBSA 21 0. 1 Bar)tailed God\~it BTGO 6 0. 1 Wnite)rumped Sandpiper ~JRSA 4 0. l Rock Sandpiper ROSA 1 o. 1 Unidentified Calidris spp. 125 0.8 TOTAL 15,713 Table 3. Estimated abundance of shorebirds in littoral habitats of the Colville River delta. Entries are the average number of birds present on the delta during the 1987 study period. Species codes are given in Table 2.

AVERAGE NUMBER PRESENTl PROPORTION SPECIES per km per km TOTAL OF TOTAL

DUNL 16. 1 645 2035 .53 SESA 1.26 67.7 610 . 16 HESA 0.56 32.9 344 .09 RNPH o. 13 16.2 301 .08 . PESA 0.03 6.0 129 .03 STSA 0.01 3.5 83 .02 REPH o. 14 7.5 67 .02 BBPL D. 13 6.9 61 .02 LGPL 0.01 2.2 49 .01 RUTU 0.09 4.9 46 .01 uwo 0.02 ;::.3 42 .01 Other Species 0.06 3.0 24 .01 All species 18.7 804 3818

1 The 1st column reports birds per linear km of shoreline, the znd column reports birds per square km (~ean for the entire littoral zone). Table 4. Habitat preferences of dunlin and all other species (none of which showed significantly different preferences ) see text). Entries are estimated proportions (and SE's) of total numbers of birds occurring in each habitat.

SILT BARRENS SALT t1ARSH DISTRIBU- Terminal Subterminal Halophytic Saline Total TION OF ... Shore 1ine Shoreline Herb Grass/sedge Number

Dun lin .72 .09 .07 . 12 2035 ( . 16) (. 03) (. 02) (.03) Other . 12 .03 . 45 .40 1783 Species (. 05) ( .01) ( • 13) (. 10) Table 5. Sectional differences (see Figure 1 for locations) in total numbers (and standard errors) and proportions of dunlin occurring on terminal shoreline silt barrens.

SHORELINE TOTAL PROPORTION SECTION LENGTH (km) IWf'IBERS {SE) OF TOTAL

1 5.44 712 (254) .42 2 5.20 278 {120) . 17 3 2.56 4 (2) .00 4 4.26 487 ( 149) .29 5 1. 73 195 (44) . 12 6 1.29 1 (1) .uo Table 6. Sub-habitat preferences of shorebirds observed in saline sedge/grass tundra. Entries are densities (birds/km2), proportions of total density, and area for four sub-habitats.

SUB-HABITAT t1ARKON DEN~ITY PROPORTION AREA TYPE CODE (km ) OF DENSITY {km2)

Wet sedge a. Non-patterned 60 64 . 19 13.2 b. Polygonized 65 122 .36 1.1 Grass-sedge a. Non-patterned 70 103 .30 5.3 b. Polygonized 75 52 • 15 3.9 Table 7. Differences in shorebird use of dry and moist halophytic herb habitats. Entries are section strata, moisture, average densities (birds/km2), and area (km2).

SECTioN MOISTURE DENSITY AREA (km2L....-:...-=--..,-=-=~,..,.,..,.""""' 3 Dry 15 o. 52 3 Dry 23 0.50 4 Dry 44 0.18 3 Moist 208 0.34 4 Moist 145 0.25 Table 8. Proportions of birds observed migrating in four directions tnrough the Colville River delta summer, 1987. Bold type shows direction for each species. Species codes are shown in Table 2.

North East South West SPECIES 3150-440 450-1340 1350-2240 225-3140 N

DUNL .06 .28 .05 .61 301 SESA • 15 . 51 .22 • 12 143 WESA . 1y .27 .04 .50 26 RNPH .02 .80 .04 . 14 115 REPH . 01 .55 .08 .36 88 STSA .24 .41 .06 .29 17 LBDO .00 .77 .04 . 19 102 LGPL .23 .56 .04 • 17 52 BBPL . 15 .67 .08 . 10 61 PESA .03 .66 . 10 .21 124 RUTU .05 .64 • 09 .23 22 Table 9. Su~mary of the habitat preferences of post)breeding shorebirds occurring in the littoral habitats of Colville River delta.

PROPORTION OF ESTIMATED TOTAL . Area Proportion All Other HABITAT (km2) of Delta Species Dun 1in Species

Terminal Shoreline 2.09 .03 .44 .72 . 12 Silt Barren Subterminal Shoreline 0.52 .01 .06 .09 .03 Silt Barren Interior Terminal 38.71 .56 .00 .DO .00 Silt Barren Halophytic Herb 10.55 • 15 • 25 .07 .45 Barren Saline Grass/ 17.50 .25 .25 • 12 . .40 Sedge Tundra Table lu. Summary of the ecology of post-breeding shorebirds occurring in littoral areas of the Colville River delta.

DONINANT MEAN NIGRATION PEAK D0~1INANT SPECIES HABITAT DENSITY PEAK TOTAL DIRECTION

DUNL shoreline 18.7 Aug. l8;Sept.l 4053 west SESA herb 11.3 Aug.4 1794 east HESA saltmarsh 5.5 Aug. 14 677 west RNPH Saltmarsh 5.5 July 28;Aug.26 766 east PESA saltmarsh 2.4 July 21 389 east

STSA sedge 2.8 Aug. 11 241 ? REPH saltwarsh l.U Aug. 18 169 east BBPL saltmarsh 0.9 July 21 143 ·east RUTIJ saltmarsh 0.7 breeder 80 shoreline o. 1 Aug. 11 92 east LGPL saltmarsh 0.9 July 21 160 east LBDO sedge 1.2 Aug. 18 186 east BASA saltmarsh 0.2 July 21 44 ?

SAND ? 0. 1 Aug.26 15 ? BBSA sedge 0.2 Aug. 11 37 ? Appendices Appendix 1. Section, area, length (shorelines), habitat, and sampling intensity for each stratum. Strata are grouped by habitat. See Figure 1 for section boundaries and Figure 2 for location examples of strata. a. Terminal shoreline silt barren habitat

Stratum Section (km 2) (km) No. surveys

1 1 0.68 18.55 4 2 1 0.44 8.78 3 3 2 0,34 6.82 8 4 2 0.05 2.61 5 5 3 o. 13 2.56 8 6 4 0.35 8.51 8 7 5 0.02 1. 16 4 8 5 0.12 2.49 3 9 6 0,02 2.58 7

b. Subterminal shore 1 ine silt barren habitat

Stratum Section (km 2) ( kr.1 ) No. surveys

10 1 0.07 6.52 4 11 1 0.13 12.70 1 12 1 0.08 8.34 3 13 1 0.12 7.05 4 14 2 0.04 3.62 8 15 3 0.05 4.98 8 16 4 0.33 7.78 8 17 5 0.02 2.13 4 18 6 0.07 7.10 7 c. Interior silt barren habitats

Stratum Section (km 2) No. surveys

19 1 3.72 1 20 1 1.14 4 21 1 0.36 3 22 1 3.23 4 23 1 3.72 3 24 2 1.07 5 25 2 5.28 8 26 3 5.57 8 27 4 12.33 8 28 5 0.83 4 29 5 0.52 3 30 6 3.55 7

d. Channe 1 silt barren habitat

Stratun1 Section (km 2) {km) No. surveys

31 1 o. 14 28.5 8 32 2 0.13 25.5 8 33 3 0.10 20.5 8 34 4 0.11 21.0 8 35 5 0.01 6.0 4 36 6 0.08 15.0 7 e. Halophytic herb barren habitat

Stratum Section ( krn 2) No. surveys

37 2 2.18 7 38 3 1. 71 8 39 3 2.60 8 40 4 0.72 8 41 4 1.00 7 42 5 0.55 4 43 5 0.51 3 44 6 o.so 4 45 6 0.46 3 46 6 0.07 2 47 6 0.24 1

f. Saline grass/sedge tundra habitat

Stratum · Section (km 2) No. surveys

48 2 1.31 8 49 2 0.09 2 50 2 0.22 5 51 3 2.03 7 52 3 U.27 6 53 3 0.98 8 54 3 0.42 5 55 4 1.35 8 56 4 1.07 7 57 5 2.41 4 58 5 3.30 3 59 6 1.36 4 6U 6 1.60 3 61 6 1.09 7 Appendix 2. Estimated densities (birds/km2) and total numbers (with standard error, SE) of shorebirds occuring in littoral habitats of the Colville River delta. Species codes are shown on Table 2 of the text.

Termina 1 Subterminal Halophytic Sa 1ine Shore 1ine Shoreline Herb Grass/Sedge f1ean Tota I Mean Tota I Mean Tota 1 fvlean Total SPECIES (SE) (SE) (SE) (SE) (SE) (SE) (SE) (SE) DUNL 558 1458 72.0 188 5.00 139 9.57 250 125 322 19.6 51 1.60 42 1. 99 52 SESA 44.6 117 4.70 12 11.27 295 7. 10 186 16.8 44 1.96 5 2.16 56 1.49 39 WESA 18.4 48 3.52 10 6.59 172 4.35 114 4.31 11 1.57 4 2.45 64 0.95 25 RNPH 5.09 12 5.93 155 5. 14 134 3.52 10 1.65 43 1. 35 35 PESA l. 17 3 2.53 66 2.29 60 0.78 3 0.96 25 0.43 11 STSA 0.39 0.33 9 2.81 73 0.39 o. 11 3 0.85 22 REPH 5.48 14 U.86 22 1.20 31 4.70 12 0.36 ~ 0.47 12 Terminal Subterminal Halophytic Saline Shoreline Shore 1ine Herb Grass/Sedge !'lean Tota 1 Nean Tota 1 r~ean Tota 1 Mean Tot a 1 SPECIES (SE) (SE) (SE) (SE) (SE) (SE) (SE) (SE)

BBPL 1.57 4 3,54 10 0.91 24 0.88 23 0.39 1 1.96 5 0.25 7 0.22 6 RUTU 0.39 2 2.74 8 0.76 20 ·0.60 16 0.39 1 1.57 4 o. 18 5 0.13 3 LGPL 0.39 1 1.10 29 0.73 19 0.39 1 0.36 9 0.28 7 LBDO 0.78 2 0.38 10 1.17 30 0.78 2 0.22 6 0.51 13 BASA 1. 17 3 0.12 3 0.24 6 0.78 2 0.07 2 0.11 3 SAND 0.78 2 0.39 1 0.07 2 0.78 1 0.39 1 0.04 1 BBSA 0.23 6 0.04 1 0.01 3 0.01 1 All Species 642 1677 89.3 233 36.28 949 36.70 959 123 322 20.7 54 4.59 120 4.00 105 Appendix 3. Habitat preferneces of shorebirds in littoral habitats of the Colville River delta. Entries for each species are the estimated proportions (and SEs) of sightings occurring in each habitat. Species codes are given in Table 2 of the text. HABITAT TYPE Terminal Subterminal Halophytic Saline SPECIES Shoreline Shoreline Herb Grass/sedge Tota 1

A11 species .44 .06 .25 .25 3818 (. 08) (. 01) (. 03) (.03) DUNL .72 .09 .07 . 12 2035 ( • 16) (. 03) (. 02) (. 03) SESA • 19 .02 .48 .30 610 ( .07) ( •01 ) (. 09) (. 06) WESA • 14 .03 .50 .33 344 (. 03) (. Ol) ( • 19) ( .07) RNPH .04 • 51 .45 301 (. 03) (. 14) ( • 12) PESA .02 . 51 .47 129 (. 02) ( ~ 19) (.09) STSA . 01 .11 .88 83 (. 01 ) (. 04) (. 27) REPH • 21 .33 .46 67 ( . 18) (. 13) (. 18) BBPL .07 . 16 .39 .38 61 (.02) (. 08) (. 11 ) (. 10) LGPL .02 .59 .39 49 (. 02) ( • 18) (. 14) RUTU .04 . l 7 .43 .35 46 (.02) (. 09) (. 11 ) (.07) LBDO .OS .24 . 71 42 ( . 05) (. 14) (.31) Other • 21 .04 .38 .38 24 Species ( . 13) (. 04) ( • 21 ) ( . 21 ) Dunlin • 12 .03 .4S .40 1783 excluded (.OS) ( . 01 ) ( . 13) ( . 10) Appendix 4. Weekly average total numbers and standard errors (SE) for species occurring in the Colville River delta. Species codes are shown in Table 2 of the text.

E SPECIES 2 3 4 5 6 7 8 ALL. 918 1981 2906 5016 bl95 6026 4692 4303 {262) (432) {883) (1073) {1132 ) ( 941 ) {898) {1851 ) DUNL 53 164 350 2261 3616 4038 3295 4067 {22) (55) (203) {816) {965) (745) (872) ( 1841 ) SESA 293 679 Y18 1794 761 235 50 0 ( 105) ( 187) (342) {309) {198) (69) (39) (0) WESA 0 51 589 321 654 699 314 30 ( 0) (45) (233) (74) (239) (306) ( 129) (23) RNPH 0 229 789 129 355 308 742 159 ( 0) {126) {417) (84) ( 136) ( 108) (260) (84) LGPL 125 160 7 . 7 42 20 20 0 (40) (50) (7) (6) (27) ( 10) ( 12) ( 0)

BBPL 55 143 61 59 77 32 54 29 (26) (53) ( 17) ( 21 ) (23) (17) (25) ( 15 ,. STSA 0 23 7 106 241 192 0 0 ( 0) ( 12) (7) (24) (97) (86) (0) ( 0)

REPH 9 28 7 73 125 169 90 0 ( 9) ( 13) (6) (57) (69) (80) (42) ( 0) PESA 278 389 41 106 105 88 0 3 {141 ) ( 134) ( 17) ( 41 ) (33) {21) ( 0) ( 3) RUTU 96 60 85 31 92 13 26 8 (36) ( 21 ) ( 21 ) {22) (44) {6) ( 19) (6)

BASA 3 44 12 20 8 14 0 0 (3) {24) (9) {9) (5) ( 8) {0) (0) LBDO 0 u 0 0 26 186 64 0 (0) ( 0) (0) (0) ( 19) ( 71) ( 27) (0)

BBSA u 0 0 0 37 15 0 0 (U) (0) (0) (0) ( 21 ) (4) {0) {0) SAND 6 2 4 1 3 3 15 10 {6) ( 2) ( 5) ( 1 ) (3) ( 2) (8) (8) Appendix 5. Temporal changes in total numbers of individuals of each shorebird species occuring in the littoral habitats of the Colville River delta.

OUNUN 5000 4500 4000

U1 3500 0:: LoJ al 3000 ~ ;:)z 2500 ....~ 2000 0 .... 1500 1000 500 0 13 21 28 4 11 18 26 1 JULY AUGUST SEPT. SEMIPALMATED SANDPIPER 2000 ' .. 1800 1600 en 1400 ffim 1200 :::E ::>z 1000 ~ 800 e 600 400 200 0 13 21 28 4 11 18 26 1 JULY AUGUST SEPT.

WESTERN SANDPIPER 800 700

600 en 0:: l..r.J 500 m ::1 z::> 400 3 e 300 200

100

0 13 21 28 4 11 18 26 1 JULY AUGUST SEPT. REO-NECKED PHAL.AROPE 900 .. aoo

700

600 500 400 300 200 100

0+----r--~~~~~~~~~~~~~~~~~ 13 1 SEPT.

LESSER GOLDEN PLOVER 200 150 160

(I) 140 Q::w CD 120 :::1 :::::> z 100 ~ ao ~ 60 40 20 0 1 SEPT. BLACK-BEI..UEO PLOVER 200 180 160

VI 140 0: LIJ CD 120 ::1 ::>z 100 eo 0~ .... 60 40 20 0 13 21 28 4 11 18 26 1 JULY AUGUST SEPT.

JOO STILT SANDPIPER 270 240

VI 210 0::: LIJ CD 180 :I ::>z 150 ~ 120 ~ 90 60 JO 0 13 21 28 4 11 18 26 1 JULY AUGUST SEPT. REO PHALAROPE 200 180 160 140 120 100 80 60 40 20

0+-~~~~~~~~~~~~~~~~~~~~ 1 SEPT.

PECTORAL SANDPIPER 450 400 350 a::tn 300 LaJ CD ::I 250 z;:) 200 ~ ....0 150 100 50

0 13 21 28 4 11 18 26 1 JULY AUGUST SEPT. BAIRD'S SANDPIPER 50 45 40

(I) 35 ffi CD '30 ::::E ::::;, z 25 20 ~g 15 10 5 0 26 1 SEPT. LONG-BILLED DOWITCHER 200 180 160

en 140 0:: 1.1.1m 120 :I ::>z 100 ~ 80 := 60 40 20 0 1J 21 28 4 11 18 26 1 JULY AUGUST SEPT.

BUFF -BREASTED SANDPIPER 50 45 40 en J5 ffim JO :::::E z::> 25 20 0~ .... 15 10 5 0 1J 21 28 4 11 18 26 1 JULY AUGUST SEPT.

Appendix 6. Proportions of shorebird activities observed during littoral zone surveys of the Colville River delta. Species codes are shown in Table 2 of the text.

ACTI I Swim/ Tot a 1 Tota 1 SPECIES Feed Stand Sleep Preen Walk Breed Knovm Known DUNL 0.89 0.04 0.05 0.02 0.00 0.01 10110 139 SESA 0.88 0.05 0.01 0.03 o.oo 0.03 1596 274 WESA 0.89 0.03 0.06 O.Ul o.oo 0.00 970 58 RNPH o. 72 0.07 0. 01 0.01 o. 17 0.01 856 64 PESA 0.65 0. 29. 0.02 0.02 u.oo 0.01 248 103 STSA 0.86 0.06 0.05 0.02 0.00 0.01 227 15 REPH 0.64 0.05 0.00 o. 15 0.16 0.01 193 12 BBPL 0.65 0.18 0.00 0.01 0.08 0.08 192 11 RUTU 0.57 o. 16 0.00 0.00 0.00 0.26 . 159 8 LGPL 0.71 0.28 o.oo 0.00 0.00 0.01 120 17 LBDO 0.67 0.33 0.00 0.00 0.00 0.00 60 55 BASA 0.63 0. 16 0.05 0.00 0.00 o.oo 38 6 SAND 0.68 0.27 0.05 0.00 0.00 0.00 22 3 BBSA 0. 71 0.18 0.00 0.00 o. 12 0.00 17 4