English Name Pacific Loon
Scientific Name Gavia pacifica
German Name Pazifiktaucher
Spanish Name Colimbo del Pacifico
French Name Plongeon du Pacifique
 
Pacific Loon
     
Peters Family Name GAVIIDAE:Loons Order 196.0
Sibley Monroe Family Name GAVIIDAE:Loons Order 3905.0
Gill Family Name GAVIIDAE:Loons Order 1770.0
New 2013 Family Name GAVIIDAE: Loons Order 204.0
 
English Synonyms
  • Pacific Diver
Synonyms
$Colymbus arcticus Pallas,1811,Zoographia Rosso-Asiatica,sistens omnium Animalium in extenso Imperis Rossico et adjacentibus maribus,2,p.341.
Authority (Lawrence 1858)
Habitat breeds freshwater lakes on arctic & subarctic tundra and taiga, from flat to foothills,in both treeless & wooded landscapes.Prefers larger & deeper ponds with less emergent vegetation.Winter Coastal salt water;chiefly nearshore open ocean,also larger bays
Breeding "Starts May in south of range,dependent on spring thaw innorthN." (HBW,1,p.172)
Movement
Nature Of Migration In The Species
Short to medium-distance complete migrant. Evacuates breeding range during winter, shifting from freshwater inland sites in the Arctic to coastal Marchine habitats along the Pacific Coast. Majority of North American population winters in Mexico. Jehl (1990) speculated that late-winter concentrations of thousands of individuals in wing molt near productive fishing areas on the west coast of Baja California might represent a molt migration to staging areas for the northward migration. Some nonbreeding birds oversummer within the winter range.
Spring
Migration March-June. Timing varies among years and is asynchronous along the coastal migration corridor, reflecting a general shifting of the population.
Little information available on departures from Mexican wintering waters. Latest spring record from Sonora 3 May. Among 3 years when Pacific Loons were regular winter residents at San Quintín Bay on west coast of Baja California, last dates of occurrence were 24 March, 1 April, and 27 March.
Along the California coast, migration begins in late March, increases rapidly to a peak in mid- to late April, and tails off gradually through May; in some years, substantial migratory movements continue into June or even early July. During a season-long study at Pigeon Point, California, in 1977, daily northbound movement of Pacific Loons peaked at 46,770 on 22 April; during a similar study in 1979, movement peaked at 72,680 on 21 April. At Southeast Farallon Island, mean date of spring migrants observed over many years was 25 April ± 14 days SD (range 1 March-14 July), with a high count of 1853 on 24 April. Along Oregon and Washington coasts, northbound migration occurs from mid-April through mid-June. Passage rates of 2,500 loons per hour observed in early May, and small but steady northward movement observed as late as last week in June. As late as 1 June 1976, Pacific Loons streamed past South Jetty of the Columbia River at a rate of 3,000 birds/h throughout much of the day. Along British Columbia coast, timing of peak abundance of spring migrants varied among years from 1 May to 15 June.
First major arrivals in se. Alaska in early May. Migrants in Bering Sea by mid-May; passage rates of up to 132per hour at Cape Peirce by 20 May. Migrants reach arctic coast of Alaska by first week in June; peak abundance at Prudhoe Bay 3-9 June. Peak migration along Beaufort Sea coast of Alaska and Yukon 6-20 June, with substantial variability among years. Migrants reach Hudson Bay area and arctic islands of Canada by second or third week of June.
Arrive on breeding grounds approximately with thawing of wetlands used for nesting. Upon arriving in Arctic, individuals may tarry along coast and in estuaries where open water permits foraging; as frozen lakes thaw, individuals move quickly to inland tundra. Ponds are occupied as soon as sufficient water is available to enable loons to take off.
First sightings at Storkersen Point study site on Beaufort Sea coast ranged from 7 to 12 June among 5 yr, although pairs and small flocks used nearby open Marchine waters earlier. Individuals frequently observed in flight over the study area before wetlands thawed completely, suggesting exploratory movements to assess pond status.
During 7 years of study at Yukon-Kiskoswim Delta, mean date of first arrival in the area 18 May (range 12-23 May). During 2 years of detailed study, individuals first observed in ponds 5 and 7 days following regional arrival.
Timing of arrival on breeding grounds in e. Canadian Arctic vary more. First observed on Foxe Peninsula on Baffin I. on 17 June and 16 May in two consecutive years; differences in ecological circumstances which might explain such a dramatic difference were not discussed. First observed at Churchill, Manitoba, in one summer on 10 June, immediately after ice went out of the river. In subsequent summer, single bird observed on a lake on 29 May and 2 birds observed at river mouth on 10 June; river became free of ice on 11 June, and a spectacular migration took place along the river on 13 June. Peak abundance at Churchill reported as 5-12 June, with earliest migrants on 27 May. First noted at Camp Kungovik on sw. Baffin Island on 11 June, steadily increased in numbers through 23 June.
Late spring migratory influxes, thought to involve immatures and/or nonbreeding adults, observed along Bering Sea coast and along Beaufort Sea coast in Yukon. One such influx occurred late June-early July 1975 at Komakuk, Yukon, when a large nearshore lead was present; another involved an eastward movement past Nunaluk Spit, Yukon, in July 1972. Function of these movements and ultimate destination of the birds involved unknown, since individuals in nonbreeding plumages not observed on breeding grounds
Fall
Migration August-December. Toward eastern end of breeding range, migration already underway in latter part of August. On breeding grounds at Churchill, Manitoba, species observed commonly through August and occasionally into September, with latest date 3 October. At Point Barrow, Alaska, westward migration period spanned 27 August-16 September. Slightly farther west at Wainwright, Alaska, peak westward fall migration occurred around 1-20 September. Migration may begin earlier in some years: many migrants noted along Beaufort Sea coast near U.S.-Canada border on 9 August 1913. Individuals remain in sheltered bays and on open ocean along Beaufort Sea coast of Yukon until late September. Migrants common in Katmai region, Alaska, from 3 September to 7 October, around Kodiak I. from late September to mid-October, and in Prince William Sound from late September through early November.
First apparent southbound migrants, perhaps nonbreeders or failed breeders, reach Washington in August; migration generally peaks there in late October (D. Paulson pers. comm.). Along Oregon coast, southward movement begins in mid-August, generally peaks in late October and early November. Timing of fall migration in Pacific Northwest appears to vary greatly from year to year. For example, 1,200 individuals observed at Manzanita, Oregon, on early date of 20 August 1992, whereas species not widely reported from the region until November in 1965.
First arrivals reach California in September. Along central California coast near Monterey, fall migration typically spans mid-October to mid-December, peaking in mid-November. At Southeast Farallon Island, mean date of fall migrants observed over many years 11 November ± 9 dyas SD (range 17 July-18 December), with a high count of 4,000 on 15 November. Migration traffic rates of 600-800 individuals/h may continue off n. California as late as mid-November. Off San Diego, California, fall migrants begin arriving in September or early October. Little information available on timing of arrival in Mexican wintering waters; earliest fall arrival date for Sonora is 8 November, and species abundant at Puerto Peñasco, Sonora, by 24 November. Among the 3 yr when Pacific Loons were regular winter residents at San Quintín Bay on west coast of Baja California, first dates of detection were 17 November, 3 December, and 30 November.
Peak fall counts: 17,000 individuals estimated passing Point Pinos, California, on 15 November 1958. In late November 1997, a flock of 120,000 Pacific Loons was massed near north end of Monterey Bay.
Away From Pacific Coast
Rare transient throughout interior of w. North America, especially in late fall and early winter. Recorded along lower Colorado River mainly late October-March. In e. Washington, e. Oregon, and Idaho, most records 17 October-4 December. In Montana, all but 2 of 14 records 11 October-22 December. In Colorado, mostly recorded late October-early December. Less frequently recorded in western interior states during spring than during fall. For example, in Colorado considered "rare to uncommon" during fall and early winter but "casual" during spring. Most eastern states have also recorded vagrant Pacific Loons, with records ranging throughout year, but with late fall-early winter records predominating, especially along Atlantic Coast (e.g., of 7 New Jersey records accepted by that state's bird records committee, 5 from 15 November-12 December, 1 from late winter, and 1 from summer.
Migration Routes
Northbound spring migrants are common along north Pacific coast of Baja California, at least as far south as San Quintín, 280 km south of San Diego. First stage of spring route used by individuals wintering on Gulf of California remains a mystery. Anecdotal evidence suggests individuals wintering on the Gulf travel overland to Pacific Coast before proceeding northward. Pacific Loons often encountered in migration at Puerto Peñasco, Sonora, suggesting that some individuals "bottle up" at north end of Sea. However, the extreme rarity of spring vagrants on the Salton Sea (only 2 records reported in 1981) suggests that very few or no loons proceed northward into inland s. California from the Gulf of California. Several flocks of Pacific Loons observed flying overland toward the Pacific Ocean from the headwaters of the Sea during the 16-20 April period. All flocks were heading due west from San Felipe over barren deserts and toward high mountains. Birds were observed only around sunrise; none were seen later in the day despite careful observations. Although the implied route to the Pacific Ocean is over 160 km, it runs over barren deserts and high mountains with a minimum height of nearly 1 km. One other historical observation directly supports a trans-peninsular migration route: immediately following a severe storm on 7 April, three Pacific Loons appeared on a mountain ranch at San José, due west of San Felipe and midway across the peninsula.
From the San Diego region to the Point Conception, Santa Barbara Co., area of California, some migration occurs along the immediate coast, but many migrants take a short-cutting route well offshore across the Southern California Bight and past the Channel Islands. As a result, large spring migrations are rarely evident along the s. California coast; for example, a spring maximum of only 500 has been reported from San Diego. From Point Conception to Oregon, migration proceeds along the immediate coast or slightly offshore, often in a spectacular fashion. Coastal migration is also often in evidence along the coasts of Washington and British Columbia, but it is unknown whether all Pacific Loons thence proceed coastally or whether some or most birds take an overwater short-cut across the Gulf of Alaska. On surveys off Grays Harbor, Washington, individuals occurred from shore to at least 185 km offshore in Apr 1977.
Farther north, the picture concerning migration routes is less clear. At Point Dall on the Bering Sea coast of the Yukon-Kuskoswim Delta, Pacific Loons never passed in numbers and were thought to have arrived from some other route than by along the coast. Along the Beaufort Sea coast of Alaska and Yukon, most spring migration is eastward. However, seasonal counts of migrating loons passing a vantage point on the Beaufort Sea coast tallied just 295 and 200 Pacific Loons in 2 springs, though another 546 and 1,114 unidentified loons likely included a good proportion of Pacifics. These small numbers (relative to spring counts of 450,000-1,000,000 obtained in central California could be consistent with an overland route between the Pacific Coast and n. Canada, but may also simply reflect a more broad-front character to the migration along the Beaufort Sea coast, which results because the ice-covered nearshore sea and snow-covered coastal plain render the coast inconspicuous as a leading line for migrants. Other types of circumstantial evidence have been cited in defense of speculations about the existence of overland migration routes. According to Palmer (1962), the phenology of spring migration suggests that some birds may undertake a considerable overland flight from the arctic coast of Canada to the southwest shore of Hudson Bay. McLaren et al. (1977) even argued that some birds may bypass the Bering and Beaufort Seas entirely by taking a direct overland route from the Pacific coast to the Canadian Arctic, because birds arrive in s. Hudson Bay before the north coast of Canada is free of ice. Nevertheless, no direct evidence yet confirms the existence of any major overland migration route through Alaska or Canada during the spring.
Fall migration routes from the breeding grounds are poorly known. Some eastward fall migration has been observed in the Arctic, hinting at possible overland migration. For example, 68% of 263 fall migrants seen in 2 yr along the Beaufort Sea coast of Yukon were flying east rather than west, and migrating flocks were observed traveling southeastward along the Amundsen Gulf coast at Holman on Victoria Island in September. Pacific Loons are regular but uncommon inland transients south of the breeding grounds (e.g., in s. Saskatchewan), also suggesting that some individuals use a more direct route over land. The first strong evidence supporting a direct overland route was the observation of 1,410 Pacific Loons migrating westward in tight flocks over Pine Pass, ne. British Columbia, on 4 October 1998.
In contrast to the spring, when continuous ice cover diminishes the efficacy of the coast as a leading line and eastward migration along the Beaufort Sea coast is essentially broad-front in character, fall migration along arctic coasts is more pronounced and concentrated along the coastline. For example, Timson (1976) re-corded 50,000 loons, including many Pacifics, migrating west past Point Barrow 27 August-16 September. Some birds apparently travel well offshore over the Bering Sea, since Pacific Loons are seen regularly in fall on the Pribilof Islands. From Washington to s. California, migration is primarily over the continental shelf on a relatively broad front, without the spectacular concentration along the immediate coast as in the spring. During November surveys off n. California, more than 10 times as many were observed over shelf waters than over the continental slope; most birds were 5-50 km offshore, but birds were detected as far as 110 km west of Monterey. The more broad-front character of Pacific Loon migration along the central California coast in fall than in spring is illustrated by counts of migrant loons from Southeast Farallon Island, 45 km offshore: over many years of monitoring, total counts of Pacific Loons were 8,046 in spring and 23,248 in fall. Because of the orientation of the s. California coastline, loons traveling southward from the Point Conception area diverge from the coastline and may spread across a broad front; fall migrants off s. California were most common within 40 km of the s. California mainland, but were detected as far offshore as Tanner Bank, 165 km southwest of Los Angeles. No information is available on the route by which birds get from the Pacific Coast to the Gulf of California
Thanks to Russell, Robert W. 2002. Pacific Loon (Gavia pacifica), The Birds of North America Online (A. Poole, Ed.),species no.657a