OTHER CRITICAL ENVIRONMENTAL 

 REQUIREMENTS 



In regions where nesting sites are scarce, con- 

 siderable modification of the winter and fall feed- 

 ing territories probably takes place when they are 

 converted into breeding territories. Presumably in 

 reorganizing breeding territories into fall and win- 

 ter feeding areas, one or the other of the adults 

 keeps possession of the nesting locality, while the 

 other members of the family seek territories un- 

 occupied by shrikes, and which, in some cases, 

 may be suitable only for winter and fall occu- 

 pancy. Size and shape of territories depends on 

 the vegetative types present, the concentration of 

 food supply, the provision of nest sites, the local 

 abundance of the species and local physical bar- 

 riers (Miller 1931), as well as on the age, sex, and 

 physical condition of the bird. 



POPULATION AND TRENDS 



No more than 16 individuals were seen from 

 1-5 and 8-9 May 1974 (Stewart and Clow 1974). 

 Specific records were: 2 May (4); 4 May (5-6); 5 

 May (1 feeding fledgling) (Stewart and Clow 1974). 



Formerly, L. I. mearnsi was rated by some 

 authors as "fairly common," but the total popula- 

 tion has always been small (Grinnell and Miller 

 1944). Long ago, it was considered tolerably com- 

 mon; that is, 2 or 3 could be generally seen during 

 an hour's walk, but they were very shy and hardest 

 to secure of any bird on the island (Grinnell 1897 ; 

 Meams 1898). They were reported fairly well 

 distributed over the whole island, but extremely 

 shy by Linton (1908). In especially favored little 

 canyons, several pairs would congregate. Two 

 pairs were found breeding not 100 m apart, while 

 a third was found within 0.4 kilometers (Howell 

 1917). 



Causes of shrike mortality on San Clemente 

 are unknown, although some, particularly of 

 nestlings and juveniles, is undoubtedly caused by 

 predatory birds and mammals. Percentage of first 

 year birds in samples of winter and spring popula- 

 tions is only about 36%, by far the smallest per- 

 centage of all races except anthonyi, another 

 island form (most races have 50% or more im- 

 matures). This indicates a relatively poor repro- 

 ductive rate in the island populations. It may indi- 

 cate a lower population loss than mainland birds, 

 but it also shows the vulnerability of island birds 

 to any change in mortality rate or reproductive 



potential (Miller 1931). 



FOOD AND FORAGING BEHAVIOR 



Shrikes hunt quite late in the evening and 

 early in the morning, at least in warm weather. 

 They are opportunists, living on the most abun- 

 dcmt and readily obtainable supply of animal food, 



including all kinds of insects and other arthropods, 

 small reptiles, birds, and mammals that they can 

 capture. One was observed carrying a young 

 house finch with the adult house finch in pursuit 

 on 5 May 1974 (Stewart and Clow 1974). If there 

 is an infestation of a particular kind of insect, 

 shrikes will concentrate on that food (Miller 1931). 



The method of hunting is to perch on objects 

 from 6 in (15.24 cm) to 6 ft (1.83 m) above the 

 ground where prey may be seen clearly. Oc- 

 casionally the bird hops about in search of animals. 

 If prey is not secured from a certain post within a 

 minute or two, it moves on to another part of the 

 territory. Passive hunting has been noted com- 

 monly during a large part of the day at times 

 other than when feeding young. A less common 

 method of feeding is capturing insects in the air 

 (MUler 1931). 



Dead prey is impaled on a thorn, twig, splin- 

 ter, or other sharp structure, or eaten almost im- 

 mediately, depending on its size. If the shrike is 

 hungry when large prey is impaled, it eats all it 

 can— as much as 7 g at one feeding. Then the re- 

 mainder is left hanging for later feedings, which 

 usually continue until the last morsel is eaten. 

 The practical value to shrikes of impaled food 

 older than a few days is slight, as dry or spoiled 

 food is not eaten (Miller 1931). 



REPRODUCTION 



A set consists of five or six eggs. Eggs vary 

 from dull white to either light neutral gray or 

 buff, covered with small spots of neutral gray, 

 yellowish brown and umber, with occasional fine 

 black scrawlings near the large end. 



Several sets have been found in March, and 

 young are commonly found out of the nest at the 

 end of March, indicating that eggs are present in 

 February. Incubation usually starts with the lay- 

 ing of the next-to-last egg; it is performed solely 

 by female. The male feeds the female during in- 

 cubation, either on or off the nest. Incubation 

 lasts about 16 days. Twenty days is the normal 

 time for young to remain in nest. Parents con- 



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