Shorebird Temporarl and Spatial Use Patterns Survey, Bristol Bay Coast

Home , Kvichak River, Nushagak Bay, Nushagak Peninsula

U.S. Fish & Wildlife Service

SHOREBIRD TEMPORAL AND SPATIAL USE PATTERNS SURVEY, BRISTOL BAY COAST, APRIL - OCTOBER 2012

Susan E. Savage and Kevin J. Payne

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December 2013

Photo: Robert Blush

Alaska Peninsula / Becharof National Wildlife Refuge PO Box 277 King Salmon, AK 99613

The mission of the National Wildlife Refuge System is to administer a national network of lands and waters for the conservation, management and where appropriate, restoration of the fish, wildlife, and plant resources and their habitats within the United States for the benefit of present and future generations of Americans.

KEY WORDS: Aerial Surveys, Coastal Surveys, Bristol Bay, Kvichak Bay, Nushagak Bay, Shorebirds

Photo: Black-bellied plovers on the Kvichak Bay beach near Naknek, Alaska, July 2008.

Suggested Citation:

Savage, S.E. and K.J. Payne. 2013. Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012. USFWS, Alaska Peninsula/Becharof NWR Report, King Salmon, Alaska.

CONTENTS CONTENTS ...... iii

List of Figures ...... iv

List of Tables ...... iv

List of Appendices ...... v

ABSTRACT ...... 1

INTRODUCTION ...... 1

STUDY AREA ...... 4

METHODS ...... 5

Field Methods ...... 5

Summarizing Results ...... 6

RESULTS ...... 6

Survey Summary ...... 6

Shorebird Abundance ...... 7

Shorebird Distribution ...... 9

Landscape-Level Events ...... 16

Incidental Cranes and Marine Mammals ...... 16

Project Costs ...... 18

DISCUSSION ...... 18

Shorebird Abundance, Composition and Habitat ...... 18

Recommendations for This Survey ...... 22

Recommendations for Future Investigation ...... 22

ACKNOWLEDGEMENTS ...... 22

LITERATURE CITED ...... 23

iii

List of Figures Figure 1. Survey locations and general geography for the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012...... 5

Figure 2. Shorebird detections for all surveys by flock size, for the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012 ...... 10

Figure 3a. Shorebird detections for April and May 2012 surveys by flock size, Bristol Bay Coast ...... 11 Figure 3b. Shorebird detections for July and August 2012 surveys by flock size, Bristol Bay Coast...... 12 Figure 3c. Shorebird detections for September, October, and November surveys by flock size, Bristol Bay Coast ...... 13

Figure 4a. Point density (density of observations) distributions for all shorebird detections, for the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012 ...... 14

Figure 4. Kernel density (density of observations weighted by flock size) distributions for all shorebird detections, for the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012 ...... 15

Figure 5. Barometric pressure (inches Hg) as recorded at the King Salmon NWS weather station during the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012...... 16

List of Tables Table 1. Shorebirds found in the Bristol Bay Watershed (From Brna and Verbrugge 2013) ...... 3

Table 2. Summary of date, time, conditions, observers and equipment used during the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012...... 7

Table 3. Summary of shorebird counts by size versus date during the Shorebird Temporal and 8patial Use Patterns Survey, Bristol Bay Coast, April - October 2012...... 8

Table 4a. Summary of shorebird counts by survey section versus date during the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012...... 8

Table 4b. Summary of shorebird counts per km of Bristol Bay survey section April - October 2012...... 9

Table 5. Summary of sandhill crane counts by survey section versus date during the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012...... 17

Table 6. Summary of beluga whale counts by survey section versus date during the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012...... 17

Table 7. Historic aerial survey data including shorebird counts, Bristol Bay Coast ...... 19

List of Appendices Appendix I. Constructing Point and Kernel Density Estimates with Shorebird Data...... 28

ABSTRACT In 2011 seven Alaska Native Tribes requested the Environmental Protection Agency (EPA) assess the impact of metal mining in the upper Kvichak and Nushagak drainages, especially to salmon resources and to species that were heavily dependent on marine derived nutrients. EPA requested US Fish and Wildlife Service prepare background information regarding some of these species; subsequently USFWS identified shorebirds as a group of interest. To better quantify shorebird use patterns along the Bristol Bay marine coast, biologists from the Alaska Peninsula/Becharof NWR conducted twelve coastline aerial surveys during the ice-free season (27 April – 24 October) of 2012 to document shorebird temporal and spatial distribution. The survey included the Bristol Bay coast from Coffee Point (north of Egegik) to Cape Constantine (tip of Nushagak Peninsula). Small shorebirds (peeps, primarily Calidris spp.) accounted for 87% of the observations. During spring migration, shorebird counts peaked in early May (37,530 birds) while fall migration had two peaks in late September (20,536 birds) and in early October (30,373 birds). Shorebird numbers were lowest in late May (69 birds) and on the first survey (566 birds). The highest count and concentration of birds were found on the Kvichak River to Clarks Point section (62% of birds, 52 birds/km/survey). Areas of high concentration (“hot spots”) varied by season and included the tidal flat south of Cape Chichagof, Big Flat near Johnston Hill, east and west sides of upper Kvichak Bay, Halfmoon Bay, Schooner Bay, and the mudflat between Snake and Igushik Rivers. Recommendations for further study are identified.

INTRODUCTION In 2011 the USFWS Region 7 Conservation Planning Assistance Branch, Fisheries and Ecological Services Division prepared a report on the Wildlife Resources of Nushagak and Kvichak River Watersheds, Alaska (Brna and Verbrugge 2013) as part of the Bristol Bay Watershed Assessment that was subsequently presented to the Environmental Protection Agency and is currently still in review. This action was in response to a request from seven Alaska Native Tribes to assess the impact of metal mining in the upper Kvichak and Nushagak drainages, especially to salmon resources and to species that were heavily dependent on marine derived nutrients. One species group that was identified in the watershed assessment was shorebirds. Shorebirds make use both of the Bristol Bay marine coast especially during migration and the Bristol Bay terrestrial environment for breeding. The following has been excerpted from Brna and Verbrugge (2013) to explain the significance of shorebirds to this issue and the reason we are conducting this survey. Refer to the paper for more details.

“Alaska intertidal areas, particularly Bristol Bay estuaries, serve two functions for shorebirds. First, during late summer through autumn, the majority of the shorebird populations that nest in western Alaska move to the benthic-rich intertidal communities of Bristol Bay, where ample food supports them while they complete their molt and fatten for autumn migrations. Winter destinations include sites throughout north, Central and South America, the central Pacific islands, and Australasia. Second, during spring, hundreds of thousands of shorebirds migrate to their western Alaska breeding grounds from staging grounds on the Copper River Delta and estuaries of Cook Inlet, passing through a broad lowland corridor (the Lake Iliamna corridor) at the base of the Alaska Peninsula, linking Kamishak Bay in lower Cook Inlet to upper Bristol Bay.

In most years, the migration through this corridor is direct, but in years with late spring or adverse weather conditions, birds stop in large numbers at Bristol Bay estuaries until conditions improve farther west (Gibson, 1967; Gill and Handel, 1981; Gill and Tibbitts, 1999). Two major estuaries in the area, Nushagak and Kvichak bays, have been recognized as Western Hemisphere Shorebird Reserve Network sites (Western Hemisphere Shorebird Reserve Network, 2011).

Thirty of 41 (> 70%) of the shorebird species or subspecies that regularly occur in Alaska each year can be found in the Bristol Bay watershed (Alaska Shorebird Group, 2008); 21 of these 30 regularly nest there (Table 12)1. Shorebird populations worldwide are showing steady declines (Stroud et al., 2006), with causes most often attributed to loss or alteration of habitats and environmental contamination. Fourteen species that regularly occur in the Bristol Bay watershed have been ranked by the Alaska Shorebird Working Group (2008) as being of high conservation concern.”

Brna and Verbrugge (2013) also provide a review of the shorebird studies previously conducted in the Bristol Bay region. This includes: inventory in the Iliamna Lake area (Williamson and Peyton, 1962), research from the Outer Continental Shelf Environmental Assessment Program (OCSEAP) (Arneson, 1978; Gill et al., 1977; Gill et al., 1978), waterfowl studies that also collected shorebird data (Mallek and Dau, 2011), inventory in the adjacent Kilbuck and Ahklun Mountains, and coastal areas from Kuskokwim Bay to Togiak (Petersen et al., 1991). Recent inventories include avian surveys in Lake Clark National Park and Preserve and Katmai National Park and Preserve (Ruthrauff et al., 2007); by the USFWS (targeting lowland areas of the northern Alaska Peninsula, Savage and Tibbitts, In prep); by the Pacific Shorebird Migration Project2 (including satellite tracking of godwits (Limosa spp.), bristle-thighed curlew (Numenius tahitiensis), and whimbrel (N. phaeopus)) (Gill et al., 2009); using color banding (whimbrels) (L. Tibbitts (USGS), pers. comm., 9/11); and using radio tracking and attachment of geo-locators (plovers (Charadriidae)) (Johnson et al., 2004; Johnson et al., 2001; Johnson et al., 2011; Johnson et al., 2008).

Much of the Alaska coastline provides important habitat for shorebirds. However the areas with extensive mudflats as found on the Copper River Delta, the Yukon-Kuskokwim Delta, the Stikine Delta, and the Bristol Bay/Alaska Peninsula lagoon system (of which the Nushagak and Kvichak River deltas are part), are the most important migratory shorebird stop-over areas in the state (Gill and Handel, 1990; Isleib and Kessel, 1973; Senner, 1979). The Bristol Bay lagoon system supports thousands of individuals of numerous shorebird species; these birds undertake post-breeding migrations to the Pacific coast of North America and across the Pacific Ocean to Australia, Southeastern Asia, and Oceania. These lagoons are crucial for species that migrate directly across the ocean to Hawaii or other South Pacific islands (e.g. bar-tailed godwit [Limosa lapponica], ruddy turnstone [Arenaria interpresas]) providing the last stopover before their long overwater flights. Several species (western sandpiper [Calidris maur]), dunlin [C. alpina], and long-billed dowitcher [Limnodromus scolopaceus] build energy reserves in the lagoons before departing non-stop for British Columbia and points south. During spring migration, the Bristol

1 Table 1 in this paper. 2 A collaborative effort of nongovernmental and governmental organizations. 2

Bay lagoons are also used by shorebirds providing an essential refueling location so they can complete their migration and can begin their breeding cycle soon after arriving on their nesting grounds.

Table 1. Shorebirds found in the Bristol Bay Watershed.

Current Conservation Species Scientific name Breeding1 Trend2 Priority3 Black-bellied Plover Pluvialis squatarola yes Declining 3 American Golden-Plover Pluvialis dominica Yes Declining 4 Pacific Golden-Plover Pluvialis fulva Yes Declining 3 Semipalmated Plover Charadrius semipalmatus Yes Stationary 2 Spotted Sandpiper Actitis macularius Yes Stationary 2 Wandering Tattler Tringa incana Yes Stationary 3 Greater Yellowlegs Tringa melanoleuca Yes Stationary 3 Lesser Yellowlegs Tringa flavipes Yes Declining 4 Whimbrel Numenius phaeopus Yes Declining? 4 Bristle-thighed Curlew Numenius tahitiensis Stationary 5 Hudsonian Godwit Limosa haemastica Yes Stationary 4 Bar-tailed Godwit Limosa lapponica Yes Declining 4 Marbled Godwit Limosa fedoa Unknown 4 Ruddy Turnstone Arenaria interpres Unknown 3 Black Turnstone Arenaria melanocephala Yes Stationary 4 Surfbird Aphriza virgata Yes Declining 4 Red Knot Calidris canutus Declining 4 Sanderling Calidris alba Declining 4 Semipalmated Sandpiper Calidris pusilla Declining 3 Western Sandpiper Calidris mauri Yes Declining? 4 Least Sandpiper Calidris minutilla Yes Declining 3 Baird's Sandpiper Calidris bairdii Stationary 2 Pectoral Sandpiper Calidris melanotos Yes Declining 2 Sharp-tailed Sandpiper Calidris acuminata Stationary 2 Rock Sandpiper Calidris ptilocnemis Yes Stationary 4 or 3 Dunlin Calidris alpina Yes Declining 4 Short-billed Dowitcher Limnodromus griseus Yes Declining 4 Long-billed Dowitcher Limnodromus scolopaceus Stationary 3 Wilson's Snipe Gallinago delicata Yes Declining 3 Red-necked Phalarope Phalaropus lobatus Yes Declining 3 Species arranged in order of the 52nd supplement to the AOU check-list of North American Birds (Chesser et al. 2011) 1 Breeding status of "Yes" requires a record of breeding evidence (nest, eggs or recently fledged young) on, or within 150 km of, the Bristol Bay Watershed. 2 Curremt trends were reproduced from Morrison et al. 2006, Table 1: Estimates, Current trend. 3 Conservation Status scores were reporduced from Alaska Shorebird Plan 2008, Table 2, Conservation Category. Species in Categories 4-5 are of high concern and in category 2-3 are of low to moderate concern.

Here we provide the results from a series of coastline surveys designed to document shorebird temporal and spatial distribution of the Bristol Bay coastline between Coffee Point (north of Egegik) and Cape Constantine (tip of Nushagak Peninsula). Beyond this, the information will also be used to identify geographic hot spots (if they exist) where in the near future we can install 1-3 time lapse cameras to track the relative abundance of birds with respect to time of day, tide level, and season.

STUDY AREA Our shorebird survey area includes the upper Bristol Bay coastline from Coffee Point on the north side of Egegik Lagoon north along the east side of Kvichak Bay, west along the west side of Kvichak Bay, north into Nushagak Bay, and south along the east side of the Nushagak Peninsula to Cape Constantine(Fig. 1).

The interaction between the shallow basin of the Bay and the twice-daily tidal fluctuation shapes the physiography of the upper Bristol Bay coast. Tides can exceed 10 m, and at least once daily exceed 5 m. These features interact with the numerous river deltas, including the Igushik, Snake, Wood, Nushagak, Kvichak, Naknek, and Egegik to form an expansive intertidal zone dominated by unvegetated sand and mudflats. The intertidal zone also includes vegetated substrate at Nushagak Bay. These intertidal areas, the Bristol Bay estuary itself, and other nearby river mouths with extensive mudflats along the Alaska Peninsula characterize the estuarine portions of the region. Conservative estimates3 of intertidal habitat measure approximately 500 km2at Kvichak Bay, 220 km2 at Nushagak Bay, and 40 km2 in Egegik Bay. In winter, substantial shore ice forms along the coast and sea ice moves through the area with the tides. The supralittoral (splash) zone varies from gradually sloping unvegetated or sparsely vegetated shore, to sand and bluffs (Pleistocene era moraines, dunes and outwash features) up to 20 m in height.

Beyond the shore zone, the region is characterized by a mosaic of wetland and tundra habitats, punctuated with low and tall shrub communities, located primarily along drainages. At higher elevations are spruce, mixed spruce, birch or cottonwood forests that give way to ericaceous dwarf shrub or sparsely vegetated substrates in the alpine zone.

The area is sparsely inhabited by people with the communities of Egegik, South Naknek, Naknek, Levelock, Ekuk, Nushagak, Clarks Point, and Dillingham being within or close to the area surveyed. Commercial set-net cabins are interspersed along the entire coastline with large commercial operations at most of these villages and also at Big Creek between Egegik and Naknek. Bristol Bay supports the largest commercial red salmon fishery in the world.

3 Mudflats digitized from USGS 1:250:000 maps. 4

Figure 1. Survey locations and general geography for the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012. A continuous survey was flown from Coffee Point to Cape Constantine. Location of the proposed Pebble Mine Site and other mining claims shown.

METHODS

Field Methods Refuge Wildlife Biologist or Biological Science Technician (either one or both of the authors) flew aerial surveys in a Refuge aircraft (a Found Bush Hawk, Piper Cub, or Aviat Husky) on wheels or floats with Refuge Wildlife Specialist\Pilot Finley or Federal Wildlife Officer\Pilot Wittkop. Surveys were scheduled about every two weeks except in June when shorebird numbers were anticipated to be low. Survey altitudes varied between 65 – 100 m above ground level (AGL). Conditions usually included no to light wind, good visibility and little precipitation. The primary observer used the program Moving Maps to voice record observations coordinated with GPS locations later used to map flock locations. The

secondary observer, if present, used paper notes and tallied birds by section. Shorebirds were not identified to species, but rather were characterized by size. Size classes were defined as follows: small (peeps [Calidris spp.], sanderlings [Calidris alba], phalaropes [Phalaropus spp.], turnstones [Arenaria spp.], rock sandpipers [C. ptilocnemis]; species < 25 cm length), medium (plovers, dowitchers [Limnodromus spp.], yellowlegs [Tringa spp.]; species 25 -35 cm length) and large (godwits, curlews [Numenius spp.], whimbrels; species > 35 cm length). Flock sizes were estimated.

Further details of the study methods are outlined in the Bristol Bay Watershed Shorebird Migration Phenology and Habitat Use along the Marine Coastline Inventory Protocol (USFWS 2012) for the Alaska Peninsula/Becharof NWR.

Summarizing Results Back in the office, we transcribed the Moving Maps voice files and input the data into an Excel spread sheet with a worksheet for each day of survey. An All Data worksheet was also created with all observations. We used ArcGIS 10.0 (SP 3 or 5) to delineate the geographic area into five sections: Coffee Point to Naknek, Naknek to Kvichak River, Kvichak River to Clarks Point, Clarks Point to Snake River and Snake River to Cape Constantine. We summarized observations by date and shorebird size, and by date and survey section. We then used the Point Density and the Kernel Density functions of ArcGIS 10 (See Appendix I) to construct density features around observations.

We also summarized information about two non-target species: sandhill crane and beluga whales. We began noting cranes during the 17 May survey. Whale data were forwarded to the NOAA-National Marine Fisheries Alaska Regional office. For weather conditions, we obtained information from Weather Underground monthly history (e.g., http://www.wunderground.com/history/airport/PAKN/2012/4/18/MonthlyHistory.html) for the King Salmon weather station for the dates of the survey period.

RESULTS

Survey Summary We completed 12 surveys between 27 April 2012 and 24 October 2012 (Table 2). Actual time on the survey route varied between 90 and 160 min with the longest survey (14 August) due to computer failure and turning back to resurvey one section. On 17 May we did not complete the section from Snake River to Cape Constantine because a plane from Dillingham was overdue and we broke off our survey to conduct a search for the aircraft. Survey length (hours) varied by aircraft. Excluding 17 May, surveys in the Found Bush Hawk averaged 1hr 43min (n = 4) while in the Cub or the Husky (not including 14 August) surveys averaged 2hr 9min (n=6). We attempted to begin the surveys about 2 hours after high tide at Naknek. Our actual start time averaged 2hr 4min after high tide at Naknek (range: 1hr 21min - 2hr 43min). Our finish time averaged 3hr 58min after high tide at Protection Point (range: 3hr 1min – 4hr 39min). Survey conditions were generally good. While not recorded, glare occasionally interfered with our ability to detect shorebirds, especially if the birds did not flush. Because daily tide levels are variable by more than 3m and are influenced by wind speed, direction and recent weather

events, beach exposure during surveys could not be controlled. In general, tidal exposure was similar through the surveys.

Table 2. Summary of date, time, conditions, observers and equipment used during the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012.

High Tide High Tide Protection Survey Survey Primary Second Date Naknek Point Start End Observer1 Observer Pilot2 Plane3 Sky4 Wind5 27-Apr 8:46 8:53 10:33 12:40 SES - JW FW PC LT 9-May 6:46 6:53 8:56 11:01 KJP - JW HW OC LT 17-May 13:00 13:07 15:43 17:21 SES KJP JW FW OC MW 31-May 10:39 10:46 13:14 14:44 SES - PF FW OC MW 10-Jul 8:55 9:02 11:09 13:07 SES - JW HF OC MW 25-Jul 7:45 7:52 9:33 11:17 SES KJP PF FF PC LT 14-Aug 11:54 12:01 13:54 16:34 SES - JW HF OC MW 27-Aug 10:51 10:58 12:59 14:58 SES - PF HF MC MW 13-Sep 12:18 12:25 13:52 15:26 SES KJP PF FW OC LT 28-Sep 14:17 14:24 15:38 17:53 KJP - JW HF PC LT 11-Oct 11:17 11:24 13:20 15:41 KJP - JW CW PC MW 24-Oct 11:10 11:17 13:35 15:56 KJP - JW CW PC MW 1 Observers: SES - Susan E Savage, KJP - Kevin J Payne 2 Pilots: JW - Jim Wittkop, PF - Pete Finley 3 Plane:first letter designates Aircraft (F - Found, H - Husky, C - Cub), second letter designates landing gear (W - wheels, F - floats) 4 Sky: PC - partly cloudy, OC - overcast, MC - mostly cloudy 5 Wind: LT - light, MW - moderate

Shorebird Abundance Shorebird numbers varied markedly throughout the survey period. Shorebird counts peaked in early May (37,530 birds) and then again in late September (20,536 birds) and early October (30,373 birds; Tables 3, 4a). We counted moderate numbers of birds in mid-July (10,381). The surveys with the smallest counts included 31 May (69 birds) and 27 April (566 birds). Most shorebirds fell into the “small” category (86.8%) with just 6.2% in the medium and 4.4% in the large category. We were unable to categorize 1% of birds by size.

With regard to location, the highest numbers and concentrations (after correcting for section length; Tables 4a, 4b) of birds were detected on the Kvichak River to Clarks Point section (62% of birds, 52 birds/km/survey), followed by the Naknek River to Kvichak River Section (10% of birds; 39 birds/km/survey), and the Coffee Point to Naknek River section (23% of birds; 33 birds/km/survey). The Snake River to Cape Constantine hosted only 4% of birds and averaged 7 birds/km/survey, while we detected less than 1% of birds (2 birds/km/survey) on the Clark’s Point to Snake River section. Given that only 4% of all birds were detected on the Snake River to Cape Constantine section, we probably missed few birds when this leg was not surveyed on 17 May. The high birds/km/survey for the Kvichak to Clarks Point section was driven particularly by the 9 May, 28 September and 11 October surveys. On 9 May surveys concentrations were also high on the Naknek to Kvichak section, and on 10 July and 24 October concentrations were higher on this section than on the Kvichak to Clarks Point Section. On 14

August the Egegik to Naknek Section hosted the highest concentration of birds and on 11 October this section hosted the second highest concentration.

Table 3. Summary of shorebird counts by size versus date during the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012.

Small- Survey Date Size Unkn Small Phalarope Medium Large Total 27-Apr 6 425 130 5 566 9-May 35,590 1,898 42 37,530 17-May 911 103 27 1,041 31-May 38 19 12 69 10-Jul 15 4,961 580 1,483 3,342 10,381 25-Jul 40 422 1,561 1,173 3,196 14-Aug 295 4,051 1,028 403 5,777 27-Aug 65 880 608 293 1,846 13-Sep 280 1,545 289 130 2,244 28-Sep 300 20,111 125 20,536 11-Oct 220 29,980 173 30,373 24-Oct 5,219 105 5,324 Total 1,221 104,133 580 7,522 5,427 118,883

Table 4a. Summary of shorebird counts by survey section versus date during the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012.

Coffee Point Naknek River Snake River to to Naknek to Kvichak Kvichak River Clarks Point Cape Survey Date River River to Clark Point to Snake River Constantine Total Approx Length (km) 70 26.6 118 39.1 63.5 317.2 27-Apr 226 335 5 566 9-May 6,013 5,950 23,787 335 1,445 37,530 17-May 107 197 725 12 No Survey 1,041 31-May 13 53 3 69 10-Jul 4,718 2,502 2,844 317 10,381 25-Jul 816 424 1,929 27 3,196 14-Aug 2,136 98 3,303 240 5,777 27-Aug 670 361 355 460 1,846 13-Sep 499 60 40 100 1,545 2,244 28-Sep 923 102 18,919 27 565 20,536 11-Oct 9,948 1,855 18,263 10 297 30,373 24-Oct 1,685 895 2,691 53 5,324 Total 27,754 12,444 73,244 729 4,712 118,883 Percent Total 23.3% 10.5% 61.6% 0.6% 4.0%

Table 4b. Shorebird counts per km of Bristol Bay survey section, April - October 2012.

Coffee Point Naknek River Snake River to Average to Naknek to Kvichak Kvichak River Clarks Point Cape birds/km/ Survey Date River River to Clark Point to Snake River Constantine survey Approx Length (km) 70 26.6 118 39.1 63.5 317.2 27-Apr 3 0 3 0 0 2 9-May 86 224 202 9 23 118 17-May 2 7 6 0 3 31-May 0 0 0 0 0 0 10-Jul 67 94 24 0 5 33 25-Jul 12 16 16 0 0 10 14-Aug 31 4 28 6 0 18 27-Aug 10 14 3 0 7 6 13-Sep 7 2 0 3 24 7 28-Sep 13 4 160 1 9 65 11-Oct 142 70 155 0 5 96 24-Oct 24 34 23 0 1 17 Birds/km/survey 33 39 52 2 7 31

Shorebird Distribution Maps including all of the locations of shorebird detections point to some general distributional trends (Fig. 2). Numerous shorebird sightings and larger flocks are concentrated in the following areas: tidal flat south of Cape Chichagof, Big Flat near Johnston Hill, east and west sides of upper Kvichak Bay, Halfmoon Bay, Schooner Bay, and the mudflat between the Snake and Igushik Rivers. The maps demonstrate the lack of detections in the western two survey sections encompassing the area from Clarks Point to Cape Constantine. Note, detections near the mouth of the Snake River that appear to be further out in the bay are shorebird observations during the 14 August survey demonstrating the distance the water level may retreat if surveys are conducted at different intervals after high tide.

To examine seasonal changes in shorebird use patterns, we created a map for every two consecutive surveys (Fig. 3a – 3c). Of the areas mentioned above as frequently used by shorebirds, the area of Schooner Bay showed the most seasonal fluctuation. This bay was used in the early season, very little later in May, uniformly through July and became increasingly important as the fall progressed. The seasonal maps also demonstrate that the larger flock sizes (contributing to the larger total numbers) were observed on 9 May, in September and October. Flock size is a somewhat artificial construct because observers have to call the numbers of birds in entities which may represent distinct flocks; when birds are abundant or more uniform in distribution, bird numbers may represent an aggregation of a short stretch of beach as the observer travels and needs to record observations.

Figure 2. Shorebird detections for all surveys by flock size, for the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012.

The point density tool in ArcGIS10 provides a more quantitative idea of distribution or clumping of shorebird observations. The kernel density tool refines this analysis to take into account the “size” of the point or in this case, the number of birds. This can be used to identify the locations where shorebirds were observed most frequently and in highest numbers (Fig. 4a and 4b). From the maps we identify the highest density locations (from east to west) at Big Creek just south of Cape Chichagof (tidal flat), an unnamed creek mouth just south of Johnston Hill on the Big Flat, just north of Cape Suwarof to Salmon Flats north of Naknek, from Salmon Creek southwest of Nakeen for 20 km southwest along Halfmoon

Figure 3a. Shorebird detections for April and May 2012 surveys by flock size, Bristol Bay Coast.

Figure 3b. Shorebird detections for July and August 2012 surveys by flock size, Bristol Bay Coast.

Figure 3c. Shorebird detections for September, October, and November 2012 surveys by flock size, Bristol Bay Coast.

Figure 4a. Point density (density of observations) distributions for all shorebird detections, for the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012.

Figure 4b. Kernel density (density of observations weighted by flock size) distributions for all shorebird detections, for the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012.

Bay, and Flounder Flat on the inside of Schooner Bay. These more sophisticated analyses agree with the previous conclusions, except they focus onto more specific locations. All of the “hot spots” are located on areas identified coarsely on USGS maps as tidal flats, and many are located at or near the mouths of small creeks.

Landscape-Level Events We charted the survey dates against the barometric pressure recorded in King Salmon at the National Weather Service (NWS) weather station (Fig. 5). Several surveys (27 April, 9 May, 17 May, 10 July, 11 October) occurred during decreasing or “peak” low pressure events, several (31 May, 28 September) occurred when pressure was increasing after low pressure, while others (25 July, 14 and 27 August, 13 September, 24 October) occurred during high pressure events.

Incidental Cranes and Marine Mammals Other birds and mammals were frequently observed during the survey and sometimes noted on the voice recordings. Various species of gulls and waterfowl were often present. On occasion, terrestrial mammals such as brown bear (Ursus arctos) and wolf (Canis lupus) were noted. On the 17 May survey the first author decided that we would always record sandhill crane (Grus canadensis) numbers as the birds are large, easy to see and not so numerous that they interfered with shorebird observations. Sandhill cranes were consistently noted from 17 May when we began recording them through 27 August (Table 4). On one survey, both observers counted cranes and the counts were consistent between observers. Cranes were usually in pairs with groups larger than 15 rare before 25 July. Most cranes were found between the Kvichak River to Clarks Point (~ 1.5 cranes/km/survey) with the Egegik to Naknek and Naknek to Kvichak sections having similar “densities” (~ 1 – 1.2 cranes/km/survey). Cranes were absent from the Clarks Point to Snake River section and rare from Snake River to Cape

Table 5. Summary of sandhill crane counts by survey section versus date during the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012.

Naknek Egegik to River to Kvichak Clarks Point Snake River Naknek Kvichak River to to Snake to Cape Survey Date River River Clarks Point River Constantine Total 27-Apr no count 9-May no count 17-May 12 7 98 117 31-May 28 14 66 4 112 10-Jul 18 47 119 24 208 25-Jul 59 95 39 5 198 14-Aug 357 1 305 663 27-Aug 28 447 11 486 13-Sep 0 28-Sep 0 11-Oct 0 24-Oct 0 Approx Length (km) 70 26.6 118 39.1 63.5 317.2 Total birds 502 164 1074 0 44 1784

Constantine. The counts changed with the season: ~ 115 birds on two May surveys, ~ 200 birds on both July surveys, peaked at 663 birds in mid-August, and fell to 486 birds in late August (last day observed).

We also consistently noted marine mammals, however since the pilots placed the aircraft to maximize beach viewing, the right seat observers in the Found Bush Hawk did not have a very good view of the water. In the tandem aircraft, the observer focused on the right/shore side of the aircraft. Beluga whales (Delphinapterus leucas) were often seen in shallow water by shore, and pilots also called out sightings on the left/water side which we voiced into our records (Table 6). The information about

Table 6. Summary of beluga whale counts by survey section versus date during the Shorebird Temporal and Spatial Use Patterns Survey, Bristol Bay Coast, April - October 2012.

Naknek Egegik to River to Kvichak Clarks Point Snake River Naknek Kvichak River to to Snake to Cape Survey Date River River Clarks Point River Constantine Total 27-Apr 35 35 25-Jul 265 21 286 14-Aug 65 8 5 89 167 27-Aug 1 1 13-Sep 53 2 55 28-Sep 181 181 Approx Length (km) 70 26.6 118 39.1 63.5 317.2 Total 66 8 539 110 2 725

belugas should be considered minimum counts and more informative about location than numbers of animals. We counted the greatest numbers and concentrations (when corrected for section length) of belugas along the Kvichak to Clarks Point section. Clarks Point to Snake River was the next most popular area for beluga sightings. Maps of these observations are being shared with the Alaska office of National Marine Fisheries.

Project Costs Flight costs account for the majority of this project’s budget. We flew approximately 14 hours in the Found Bush Hawk at $190/hour and 25.16 hours in a Husky or Cub at $125/hour for total flight costs of approximately $5,600. We bought a new microphone and batteries ($54) for use with Moving Maps. Other costs that are not itemized by project included staff time (Pilots and observers), staff hazard pay (observers only), staff overtime/comp time, and aircraft fuel.

DISCUSSION

Shorebird Abundance, Composition and Habitat Estimating shorebird sizes and flock numbers from an aircraft at 65-100m AGL and moving 130 – 160Kph is no easy task. The first biologist to do so in the Bristol Bay region (Arneson 1976) agrees that even size determination is difficult (Arneson 1978), and species ID but for a few larger or distinctive species is impossible. Other surveyors (e.g., Gill and Sarvis 1999) have become more skilled at this task. For our study, both observers had previous experience with aerial survey of other bird taxa, but little experience with aerial shorebirds surveys. Both observers have surveyed shorebirds on the ground. During practice with the computer program “Wildlife Counts” (Lucid Reverie LLC) both observers tended to underestimate large flocks. During flights, we found that shorebirds could be present on the beach, but undetected until they flushed. This was particularly true under sunny conditions when there was glare from wet sand or mud. Birds that did not flush may not always have been detected. Another factor influencing counts was the width of the tidal exposure. Some sections are quite wide (e.g., Big Flat near Johnston Hill – 3.5 km on USGS topo, mudflat at Schooner Bay - 2.7 km on USGS topo) and with one pass it is impossible to detect shorebirds across the entire section. We also cannot detect birds that are using the upland area versus the beach. Another factor is local disturbance. Especially during fishing season (the peak activity is from mid-June – mid-July), flocks could be displaced temporarily and missed during surveys. We both agree that the numbers represented in this report represent minimum numbers of birds.

Ground and aerial surveys specific to shorebirds along this section of the Bristol Bay coast are few. None have focused on this section of shoreline over an entire season. During the Outer Continental Shelf Environmental Assessment Program studies4 Arneson (1977) conducted seven preliminary reconnaissance surveys in the Northern Alaska Peninsula/Bristol Bay area from fall of 1975 through summer 1976 for all coastal birds5 (applicable data presented in Table 6). He conducted the first coastal

4 See http://www.arlis.org/docs/vol1/OCSEAP2/authorindex.html reports by Arneson 1976-1980 5 We included data from the Bristol Bay North section in our table which includes the western 3 sections of our survey plus the coast from Cape Constantine to Cape Newenham, and not the Alaska Peninsula North which 18

aerial avian survey by helicopter for the Northern Alaska Peninsula/Bristol in May 1977 (Arneson 1978). Other aerial surveys in the area by USFWS Migratory Bird Management office in Anchorage (primarily lead by Wildlife Biologists Rodney King, Christian Dau, and Edward Mallek, conducted in late April/early May and late September/early October and targeting emperor geese (Chen canagica), also collected information about shorebirds from 1979-2012. Spring numbers were quite variable depending on date of survey and ranged from lows of 0 birds (e.g., 4-7 May 1998, King unpublished) to highs of 7,279 (Arneson 1978) and 9,758 (1992 King, unpublished). During fall, shorebird numbers have been documented to range from 0 (e.g., 4 – 8 October 2005, Mallek & Dau 2005), 22,197 (Gill and King 1980), to 67,092 (Gill & Sarvis 1999). Note that the high count comes from an early September survey which contrasts sharply to our 2,244 birds observed on 13 September, but is closer in magnitude to our 28 September count of 20,536 birds. The highly variable nature of the shorebird counts in the emperor goose long-term data set points potentially to three sources of variation: the variation in the bird numbers (parameter of interest), the variable availability of birds to be counted (the availability of the birds, depends on tide level), and the ability of the surveyors to include non-target species (surveyor ability, volume of target species). One additional high count of 52,000 small sandpipers in October 1979 was made immediately south of our study area in Egegik Bay (Gill & Conant 1979).

Table 7. Historic aerial survey data including shorebird counts, Bristol Bay Coast.

Time Frame Method Geographic Extent Observation Reference 17-20 May Bristol Bay North (Kvichak 76 Fixed-wing to Cape Newenham) 4,566 shorebirds Arneson 1977 Coffee Point to before Etolin 3,866 shorebirds, mostly 6-May-77 Helicopter Point small & medium Arneson 1978 west side upper Kvicahk Bay to Kulukak Point 7,279 shorebirds, mostly 13-May-77 Fixed-wing (beyond Cape Constantine) small or mixed sizes Arneson 1978 Kulukak Point (W side 1,671 small sandpipers, 49 1-4 Oct. 79 Fixed-wing Nushagak) to Coffee Point black-bellied plovers Gill & Conant 1979 early Sept. 67,092 shorebirds, 94% 1997 Fixed-wing similar to our study area small Gill & Sarvis 1999 Late April/Early May 1981- Fixed-wing, target Kulukak Point (W side 1998: King Unpub., 2011 emperor goose Nushagak) to Coffee Point1 0 - 9,758 shorebirds 1992: King Unpub.2 late Sept./ 2005: Mallek & Dau Early Oct. Fixed-wing, target Kulukak Point (W side 2005; 1979-2011 emperor goose Nushagak) to Coffee Point 0 - 22,197 shorebirds 1980: Gill 19802 1 Sections 29 – 35 (7E – 8 for 1977-1992) of the emperor goose study area which closely aligns to the Bristol Bay Watershed area. 2 Emperor goose surveys, which include shorebird counts, conducted from 1979 - 2011 in spring and 1981 - 2011 in fall; reference given for high and low years (on more than one year 0 shorebirds were counted).

Ground surveys in the area and adjacent to it shed further light on species composition of migrating shorebirds in the Bristol Bay region. During Peterson’s (1991) breeding bird studies at the Kilbuck and includes the first two sections of our survey plus the rest of the Alaska Peninsula from Unimak Island. 19

Ahklun Mountain region directly west of the Bristol Bay Watershed, notes on coastal migrants were also collected. Common migrants included: black-bellied plover (P. squatarola), Pacific golden-plover (P. fulva), whimbrel, bar-tailed godwit, western sandpiper, rock sandpiper, dunlin, short and long-billed dowitchers (Limnodromus griseus and L. scolopaceus), and red-necked phalarope (P. lobatus). During ground surveys on the Nushagak Peninsula coast (MacDonald and Wachtel 1999, MacDonald 2000), dunlin were the most common species encountered. These data, and the composition data from other aerial surveys, agree with our findings regarding “species” composition. During most of the historic surveys and during our surveys, 80% or more of the birds were considered to be small shorebirds.

Peterson (1991) also chronicled fall migration timing. Migration began for some species as early as late June (black-bellied plovers), but most species began in mid-July and most of these species were noted through late September. Nushagak Peninsula surveys (MacDonald and Wachtel 1999, MacDonald 2000) began in early August through September 10 or 11 (1999-2000) with counts of hundreds to thousands of birds through this period. Dunlin, especially at Heads Estuary, showed a cyclic pattern in 2000.

Seasonal patterns of shorebird migration have been documented in other areas of Alaska, for example at Point Barrow (Connors et al., 1979), on the Yukon-Kuskokwim Delta (Handel and Dau 1988, Gill and Handel 1990), and the north central Alaska Peninsula (south of our study area; Gill and Jorgensen 1979). These studies indicate individual species may have multiple peaks due to differential timing of various ages and sexes. Incidental observations by Refuge Wildlife Biologists and local birders over the years indicate that shorebirds can be quite numerous on the Kvichak beach near Naknek during the salmon fishing season (especially beginning in early July) with numbers pulsing through in waves through the fall. This early post-breeding pulse was noted on the 10 July survey with the second highest count in this section of 2,500 birds. This is also near the peak of the fishing season, so as noted above, this may represent depressed counts due to fishing activities that frequently flush birds.

Mapping the shorebird distributions and conducting the density and kernel analysis show locations of repeated shorebird activity and preference. Arneson (1978) states that densities of shorebirds were greater in inter- and supratidal areas of Bristol Bay than similar areas of the Northern Alaska Peninsula. Unfortunately, quantitative shoreline composition data were not available at the writing of this report so more detailed analysis examining links to physical features cannot be conducted. However, one can note that many of the shorebird concentrations were associated with wider mudflats and some are located near creek or river outflows. One interesting observation is that not all concentrations are found in protected coves or bays; several occur near exposed capes.

More recent telemetry studies further support the importance of the Bristol Bay coastal zone to western sandpipers and dunlin during spring migration. Four of 132 western sandpipers radio tagged in California or Washington were detected at Kvichak Bay (n=3) or at Igushik River (n=1) in the spring of 1995 or 1996 (Bishop and Warnock 1998); two of these individuals were detected on the Copper River Delta. In 2001, 39 dunlin were similarly marked in California and Washington and two of these birds were relocated in Bristol Bay; one of these birds (detected 15 May) was later relocated on the Yukon- Kuskokwim Delta (21 May; Warnock et al., 2004). These observations suggest that from the Copper

River Delta, birds move quickly to their breeding sight. Our protracted spring counts of birds also support this assertion.

A growing body of information continues to support the theory that various species of bird’s migration strategies have evolved to be sensitive to wind patterns generated from significant weather events (see reviews found in Gill et al., 1978, Gill et al., 2005). These winds are driven by low pressure systems that are common in the Bering Sea and Gulf of Alaska in late summer and fall. Capturing the effect of pressure on the bird counts would only be possible if the counts were conducted over successive days. From a logistical perspective, since survey conditions necessitate lower wind speeds, this is likely impossible. Satellite marking birds (Gill et al., 2005, 2009) is one way to capture this information; on the ground observations at multiple locations would be an alternative method.

With regard to intertidal benthic resources available along the Bristol Bay coastline, the authors have been unable to locate any local inventory information. A study on the Copper River Delta (Powers et al. 2002) indicates Macoma balthica was the dominant infaunal organism in both number and biomass. Other common invertebrates included the amphipod Corophium salmonis and the polychaete Eteone longa. Macoma spp. were found to dominate stomach contents of dunlin (Warnock & Gill 1996) and rock sandpipers (Gill et al., 2002) in western Alaska. In western sandpipers (Senner et al., 1989) Macoma balthica, Mytilus edulis and Mya sp. along with 2 larval dipterans dominated the diet in the Cordova area of Alaska. Powers et al. (2002) further describe the growth rate and longevity of M. balthica on the Copper River Delta as being slow growing and long lived. They further elucidate its sensitivity to oil and the impact of a major oil spill on the food web of the Delta and the direct impacts to shorebirds of such an event.

The impact in Bristol Bay of a large scale mineral mine on wildlife is yet to be determined. The draft EPA Bristol Bay Watershed Assessment (2013) focuses on the impact of the mine primarily to salmon, freshwater aquatic organisms, and organisms through their dependence on marine derived nutrients. A detailed assessment of the impact of the mine on the organisms of the ecosystem awaits an Environmental Impact Statement of the project. The development of a large scale mine such as this will have a myriad of impacts on the terrestrial and aquatic environment, and the wildlife that depend on this habitat. The release of copper into the aquatic environment is but one potential impact any large- scale copper mining project. Tens to hundreds of studies have been conducted on the toxicological effects of copper on freshwater and marine aquatic organisms. While the impacts vary according to form and concentration of the copper and environmental variables, impacts have been noted to: meiofaunal density and diversity (Lee and Correa 2007, Medina et al. 2005); reproductive success (Gorski and Nugegoda 2006, Lee and Johnston 2007, Gopalakrishnan et al. 2007, Tollett et al. 2009, Khangarot and Das 2010); histological changes (Maharajan et al. 2012); bioaccumulation from macroalgae to invertebrates which affected survivorship (Roberts et al 2006); and physiological responses (Brown et al. 2004, Chen et al. 2002). Also see reviews in Grosell et al. (2007) and, Eisler (1988) and the results of long-term monitoring of mine tailings on benthic marine infaunal community (Burd 2002).

Recommendations for This Survey:

We recommend any further surveys should be conducted at 50 – 67 m AGL and as slow as possible unless this lower altitude results in flushing birds ahead of the aircraft. Continue to use Moving Maps or other voice recording software that links location and observation. Data recording requiring the observer to look away detracts from the number of birds observed.

Recommendations for Future Investigation We have identified multiple “hot spots” where shorebirds are common throughout the ice-free season. As our original intent, we recommend at least one camera is set up at one hot spot to track shorebird relative abundance over time and tide. Time includes time of day and time of year. We recommend that camera should be installed in late April and operate through late October. Photos should be taken four times per hour during daylight hours. This pattern will capture general hourly/tidal patterns allowing some resettlement after small disturbances that may occur at the “target” hourly interval.

ACKNOWLEDGEMENTS We thank the pilots that safely conducted the surveys: Refuge Wildlife Specialist\Pilot Finley, Federal Wildlife Officer\Pilot Wittkop. Thanks to the Refuge staff who provided other logistical support. Funding was provided by the Alaska Peninsula/Becharof NWR. Mary Ann Bishop (Research Ecologist, Prince William Sound Science Center), reviewed the report and provided useful suggestions and references. Supervisory Biologist Britton also provided helpful comments. Thanks to Steven Johnson, USFWS Region 7 Librarian, , Alaska Resources Library & Information Service (ARLIS), for assistance with references relevant to this report.

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Appendix I. Constructing Point and Kernel Density Estimates with Shorebird Data

Point Density – From ArcGIS 10 Desktop Help.

The Point Density tool calculates the density of point features around each output raster cell. Conceptually, a neighborhood is defined around each raster cell center, and the number of points that fall within the neighborhood is totaled and divided by the area of the neighborhood.

If a Population field setting other than NONE is used, the item's value determines the number of times to count the point. For example, an item with a value of 3 would cause the point to be counted as three points. The values can be integer or floating point. If an area unit is selected, the calculated density for the cell is multiplied by the appropriate factor before it is written to the output raster. For example, if the input ground units are meters, comparing a unit scale factor of meters to kilometers will result in the values being different by a multiplier of 1,000,000 (1,000 x 1,000).

Possible uses include finding density of houses, wildlife observations, or crime reports. The population field can be used to weight some points more heavily than others, depending on their meaning, or to allow one point to represent several observations.

Open the Point Density tool by going to Arc Toolbox/Spatial Analyst Tools/Density/Point Density.

Select the input point feature, leave population field as NONE, select the output raster, output cell size, Neighborhood = circle, and radius (map). The resulting file name PDSB12001003 provides the following information PDSB12 = Point Density ShoreBirds 2012, and the 001003 indicates the values used for the cell size (.001) and radius (.003). The specifics for cell size and radius will depend on how you want the map to look. If cell size is large then the raster cells will be large relative to the scale of interest. If the radius is large then the point density map will “spread” over the landscape and not tell you much about the precise location of the higher point density areas. Below are two examples of variation in cell size

and radius (Fig. 1 & 2). There may be some statistical analysis to help decide but the maps I made are based on field observations.

Figure 1. Point Density Estimate near Munson Figure 2. Point Density Estimate near Munson Creek using the default settings. Cells are 170 Creek using a cell size of .001 and a radius of x 340 meters and the highest density patch .0037 (tentative version). Cells are ~ 50 x 110 (darkest blue) is ~ 1000 m wide. meters and thehighest density zone is ~ 285 m wide.

Kernel Density – From ArcGIS 10 Desktop Help.

The Kernel Density tool calculates the density of features in a neighborhood around those features. It can be calculated for both point and line features.

Possible uses include finding density of houses, crime reports, or roads or utility lines influencing a town or wildlife habitat. The population field could be used to weight some features more heavily than others, depending on their meaning, or to allow one point to represent several observations. For example, one address might represent a condominium with six units, or some crimes might be weighted more heavily

than others in determining overall crime levels. For line features, a divided highway probably has more impact than a narrow dirt road, and a high-tension line has more impact than a standard electric pole.

Conceptually, a smoothly curved surface is fitted over each point. The surface value is highest at the location of the point and diminishes with increasing distance from the point, reaching zero at the Search radius distance from the point. Only a circular neighborhood is possible. The volume under the surface equals the Population field value for the point, or 1 if NONE is specified. The density at each output raster cell is calculated by adding the values of all the kernel surfaces where they overlay the raster cell center. The kernel function is based on the quadratic kernel function described in Silverman (1986, p. 76, equation 4.5).

If a population field setting other than NONE is used, each item's value determines the number of times to count the point. For example, a value of 3 would cause the point to be counted as three points. The values can be integer or floating point.

By default, a unit is selected based on the linear unit of the projection definition of the input point feature

data or as otherwise specified in the output coordinate system environment setting. If an area unit is selected, the calculated density for the cell is multiplied by the appropriate factor before it is written to the output raster.

For example, if the input units are meters, the output area units will default to square kilometers. Comparing a unit scale factor of meters to kilometers will result in the values being different by a multiplier of 1,000,000 (1,000 meters x 1,000 meters).

Increasing the radius will not greatly change the calculated density values. Although more points will fall inside the larger neighborhood, this number will be divided by a larger area when calculating density. The main effect of a larger radius is that density is calculated considering a larger number of points, which can be farther from the raster cell. This results in a more generalized output raster.

Open the Point Density tool by going to Arc Toolbox/Spatial Analyst Tools/Density/Point Density.

Select the input point feature, change the population field to reflect your survey numbers, select the output raster, output cell size, and search radius (map). The resulting file name KDSB12001003 provides the following information KDSB12 = Kernel Density ShoreBirds 2012, and the 001003 indicates the values used for the cell size (.001) and radius (.003).

The specifics for cell size and radius will depend on how you want the map to look. If cell size is large then the raster cells will be large relative to the scale of interest. If the radius is large then the point density map will “spread” over the landscape and not tell you much about the precise location of the higher point density areas. Below are two examples of variation in cell size and radius (Fig. 3 & 4). There may be some statistical analysis to help decide but the maps I made are based on field observations.

Figure 3. Kernel density estimate near Munson Figure 4. Point density estimate near Munson Creek using the default settings. Cells are 170 x Creek using a cell size of .001 and a radius of 340 meters and the high density zone is ~ 1030 .0037 (tentative version). Cells are ~ 50 x 110 m wide meters and thehighest density zone is ~ 170 m wide.

Comparisons of the default (larger cell size and radius) and selected (smaller cell size and radius) point density maps (Fig. 5) and kernel density maps (Fig. 6) are shown below. The selected settings map is layered on top of the default settings map.

Figure 5. Overlay of point density maps for Figure 6. Overlay of kernel density maps for comparison. comparison.