Strachan and others 



Chapter 23 



At-Sea and Foraging Behavior 



before dusk, birds that are both loafing or foraging will 

 coalesce into loose aggregations with much preening and 

 wing stretching (Carter and Sealy 1990; Nelson, pers. comm.; 

 O'Donnell, pers. comm.). We and Sealy (1975) have noted 

 that specific sites are consistently used for these gatherings. 

 Carter (pers. comm.), Kuletz (pers. comm.), and we have 

 observed many times that a few minutes before dark the 

 birds will begin to take off and fly inland in pairs or singly. 

 In southeast Alaska, McAllister (unpubl. data) has found 

 that these loose aggregations most often occurred offshore 

 of forests, and in waters where foraging is rarely, if ever, 

 observed. He found that birds begin landing at these locations 

 in the late afternoon. The rate of arrival increased steadily 

 until the hour before dusk, as birds were commonly seen 

 flying in and landing, with most holding fish. He observed 

 this commonly along the west shore of Admiralty Island 

 where birds arrive on flyway routes from foraging areas in 

 Icy Strait. The birds holding fish were found in a band 

 between 1-2 km from the shoreline. At dusk these birds fly 

 from the water, often climbing steeply before heading inland. 

 Simons (1980) and Hirsch and others (1981) also observed 

 murrelets holding fish just before flying inland at dusk. 



Loafing Activities 



Loafing in the murrelets involves resting on the water, 

 perhaps sleeping, along with preening and other activities. 

 During loafing, we have observed that birds appear to drift 

 with the currents, or move about without direction. We have 

 also observed vocalizations during loafing periods, especially 

 during the mid-morning and late afternoon. There are no 

 data available on the frequency of wing stretches and flutters 

 during the day, nor the function of the vocalizations. 



Flyways 



In regions of high murrelet populations in coastal British 

 Columbia and Alaska, what we refer to as "flyways" of 

 Marbled Murrelets occur. Here, hundreds to thousands of 

 birds commute between foraging and nesting areas. The 

 birds are moving distances up to 60 km (McAllister, unpubl. 

 data). McAllister has observed throughout the breeding season 

 that birds moving along these routes are most numerous in 

 the two hours following sunrise, as birds returned to foraging 

 areas. During the chick-feeding period, the same flyways are 

 again active in the night just before dawn (taking fish to their 

 young) and just after dusk (returning to foraging areas). 



Courtship Behavior 



Courtship behavior at sea has been rarely reported in 

 Marbled Murrelets. Quinlan (1984) described courtship 

 behavior involving both birds of a pair extending their necks 

 vertically and pointing their bills skyward while slowly 

 swimming towards each other. The birds maintained this 

 posture, then swam together for 15 to 30 seconds. McAllister 

 (unpubl. data) has observed courtship behavior in March and 

 April in southeast Alaska, most often in the early morning, 

 soon after birds land following dawn flights. He has recognized 



two distinct behaviors: heads-up posturing, and pursuit flight- 

 diving. The most common, heads-up posturing, involves 

 two birds taking an erect posture, necks fully extended 

 upwards, and heads tipped back, so that bills are directed 

 upward. Pairs will draw very close to one another and either 

 circle or swim forward rapidly. They may dive and then 

 resurface in the heads-up posture. If separated while diving, 

 the pair will rapidly swim towards each other in the heads- 

 up posture. Heads-up posturing may change into pursuit 

 flight-diving behavior, as one bird flies low across the water 

 pursued by the other bird. The lead bird then makes a flying 

 dive, the other following into the water and pursuing the lead 

 bird underwater until they resurface into flight again, without 

 a hesitation in wing beats. The pair may take flight and dive 

 repeatedly, as many as four times consecutively. 



Copulation has been observed only rarely on the water, 

 and may primarily occur in forests before egg laying. Quinlan 

 (1984) observed copulation at sea once on 16 May 1984. 

 Prestash (pers. comm.), recorded copulation on May 29, 

 1990 at Muscle Inlet, British Columbia. In California, 

 copulation on the water has been observed only 3 times in 

 approximately 3,000 hours of observations, mostly during 

 the breeding season (Ralph, unpubl. data). 



Disturbances 



The effects of human disturbance on murrelets at sea is 

 not well documented. Strong (in press) felt that birds were 

 very sensitive to his passing vessel. Almost all responses 

 occurred at less than 50 m from the boat. Of 4721 behaviors 

 recorded, in apparent response to passage of the boat, 1 103 

 birds dived (23.4 percent), and 725 (15.4 percent) flew. 

 McAllister (unpubl. data) observed that in Gastineau Channel, 

 near Juneau, Alaska, murrelets apparently habituate to heavy 

 levels of boat traffic. Ralph (unpubl. data) has noted that 

 birds in the San Juan Islands, Washington, allowed much 

 closer approach in boats, as contrasted to birds in waters of 

 offshore California, where boat traffic is much lighter. 



Discussion 



Documentation of the species' at-sea behavior is 

 important to the full understanding of the ecology of the 

 species. Our overview demonstrates how few data have been 

 gathered on the behavior of the bird on the ocean. Knowledge 

 of the timing and extent of different behaviors is also essential 

 to the design and implementation of at-sea monitoring 

 protocols. For instance, the response of birds to boats and 

 airplanes would greatly influence the ability of observers to 

 count birds. Also, knowledge of the percent of time spent 

 underwater is also important in determining the ability of 

 observers to detect birds from boats. 



Various observations during the breeding season suggest 

 that the birds may forage in some areas at night, and probably 

 more often at or near dawn and dusk, to procure food for 

 their chicks. Some observations of nocturnal feeding are 

 possibly related to prey tending to be closer to the surface at 



252 



USDA Forest Service Gen. Tech. Rep. PSW-152. 1995. 



