(Lanius Collurio and L. ·Cristatus, Aves) in the Zone of Sympatry A
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R 11.u1 111 l t111 n111J ef7.,,o/o;:_r. \41/. I , No. 4. 1997, p p. 537- 544. Tnm.d111ed/rom Ztw loJ,:iclte.ddi Zlmrnal. ~J /. 76. No. JO, 1997, pp. // 9.1- 120/. Ori1:11wl Rux.m m 1C-xt CopyriKIU 11) / 997 hy Kryukm~ Gun:rr. l:.'11g/ish Tnm.'ile1 1ion Cop.rriNlil Q /9CJ7 by M A l1K llt1yA·a/ /111 11rperitulica Publi.dtiu>: t R11.uiaJ. New Data on Interrelations of Red-backed and Brown Shrikes (lAnius collurio and L. ·cristatus, Aves) in the Zone of Sympatry A. P. Kryukov* and S. P. Gureev**. * Institute of Biology and Soil Sciences, Far Eastern Division., Russian Academy ofSciences. pt: Stoletiya V/adivostoka I 59. Vladivostok, 690022 Russia ** fllstitute of Biology and Biophysics, Tomsk. 634050 Russia Received August 20. 1996 Abstract-Red-hacked (Lanius collurio) and brown shrikes (L. cristatus) are clearly distinguishable species. A new map of their distribution in the zo ne of sympatry in Western Siberia is presented. According to field observation, both species have slight habitat preferences, especially in disturbed sites, and overlapping nesting periods. One of the species usually prevails in number. Despite differences in phenotypes and mating behavior, ind ucli ng vocaliza tion, they form mi xed pairs that subsequently either separute or produce fertile hybrids. The first descripti on of a hybrid male with intermediate coloration and size is provided. Distribution of intraspecific hybridi zation within the family Laniidae is discussed. INTRODUCTION RESULTS The origin and ma intenance of reproductive isola Spatial Relationships tion remain the key problem for both species theory and practice of taxonomic decisions. The forms isolated to The zone of sympatry of L. col/urio and l. cristatus has larger area than considered earlier (Mauersberger different extents are of particular interest for elabora and Portenko, 1971 ). In addition to extreme localities tion of this problem. The group of small Palearctic spe of their ranges that were described earlier (Kryukov, cies of the genus umius compose a suitable model for 1980), new map of the distributions extends the range such a study. It includes "true" species that are clearly of L. collurio eastwards (Fig. I ). Summer records have isolated in zones of sympatry (Lanius cristatus L. L. iso/Jeltinus Hempr., Ehrenb.). as well as so-call ed been made recently in Khakassia, Malaya Sya River valley; records on nesting sites were made in northern "semispec ies" with zone::; of secondary intergraclation and eastern foothills of Kuznetsky Alatau, in vi ll ages of (L. co!!uriu L.- L. plweniurroides Schai. , l. collurio Novyi Berikul', Komsomolskii, Efremkino, and Tisul' L. isabellinus speculigerus Tacz.). At the same time, in (observati ons by S.P. Gureev); and the records of males the zones of sy mpatry of even quite divergent, well-dis at May 20 and Ju11 ~ 3 in surroundings of Nazarovo City tinguishable ulllius species, hybrid individuals or in Krasnoyarskii Krai (V.S. Zhukov, pers. comm.). mixed pairs occur. This requires careful examinati on of such situations, their causes, and consequences. This It is interesting to note that this species had not been works aims at analyzing sy mpatric zones of L. collurio recorded earlier in the Kuznetsk Alatau (l.M. Zalesskii and L. criswtus, determining its boundaries and ecolog and P.M. Zalesski i, 1931). logansen ( 1935) noted that ical conditions of the contact, elucidating reproductive L. collurio range ex tends eastward only to the Salair interrelations and, in particular, factors maintaining Ridge, which is located west of the Ku znetsk Alatau. At species integrity. the same time, Khakhfov ( 1937) found these birds in large numbers in the sod-meadow zone of the Kuz netskaya Hollow. This spec ies seems to move gradually MATERIALS AND METHODS eastward, being dispersed over burned-out fo rests, Materials were collected in 1978-1984 in the zone glades, and other anthropogenic landscapes. Some of sympatry of two species·. Fragmentary observations authors indicate also dispersal of L. cristatus 250-300 were conducted iii some localities of Altai and Ku z km northward during the last 50 years and explain it in netsk Alatau mountains, stat ionary studies at 20 km terms of warming of climate and anthropogenic trans NW from Lake Teletskoc near the village of Kebezen' fo rmation of the landscape (Syroechkovski i and and in northern foothills of the Kuznetsk Alatau near Rogacheva, 1959). the village of Novyi Berikul'. We studied timing of In the majority of the localities studied in the zone arrival and occupation of territories, habitat distribu of sympatry, l. collurio prevails numerically. This con ti on. territori al and breeding relations, composition of cerns Kyzyl-Ozek, Shabalinsk, and Turochansk regions pairs. and peculiarities of nesting. Censuses of birds of the Gorny Altai (our observat ions), surround ings of were conducted in transects of unlimited width. Tomsk (S.S. Moskvitin, pers. comm.), middle reaches 537 538 KRYUKOV,GUREEV of the Ob River (A.A. Ananin, pers. comm.), surround ests, glades. and thickets on ffat slopes. In surroundings ings of Leninogorsk (Kuzmina, 1948), and many local of Kebrz.en' Village both species nest together on forest ities in the southern taiga subzone of Western Siberia edges and piles of fallen trees removed from territories (Ravkin and Luki'yanova, 1976). On the contrary, prepared for plowing (Kryukov, 1980). L. cristatus clearly prevails in the middle reaches of the Kara and Tom-Chumysh rivers in the Salairsky Ridge, In surroundings of the Novyi Berikul' Settlement, according to three-year observations hy Chunikhin northern foothills of the Kuznetsk Alati.!U, different ( 1965). Our recent observations in Kuznetsky Alatau. at stages of anthropogenic succession: felling areas. pas the eastern range margin of L. collurio, gave similar tures, hay meadows, etc .. are formed at the background results. of the main forest fo rmation, black taiga. Lanius inhabit there rarefied forests and edges with developed Habitat distribution of both species is unclear. In grass cover and shrubs, as well as shrubby meadows: general, L. cristatus is more "sylvatic" and "montane" hay meadows and pastures, felling areas of different species. According to A.A. Ananin (pers. comm) for the age with young primary frees, remains of undergrowth, floodplain of the Middle Ob in Krivosheinsky District and fallen trees (Table I). Maximum density was of Tomskaya Oblast, L. collurio has been noted in all observed there in the overgrowing glade clearing I 00- years of observation ( 1979-1983) whereas L. cristatus 120 m width made for a power transmission line only in dry years without spring flood ( 1981 and 1983). (Fig. 2). These conditions: fallen trees, bushes, and In the Northern Altai, Lanius inhabits margins of light trees on the edge, cpen areas, and hid1r.g sites h::.ve conifer forests in low hills (Ravkin, 1973), rarefied for- become suitable for Lanius. Therefore, the both species --o!. ) ........ ....... .. ,o2 .... .... .... .... , ' ' ' ', ............. 3 ,," '-o" 0 300 , .. ------- ·------ -- --·---- NEW DATA ON INTERRELATIONS OF RED-BACKED AND BROWN SHRIKES 539 of Lanius actively penetrate anthropogenic landscape adjoined one another. Therefore, both species remain in finding there optimal conditions. contact, especially in anthropogenic habitats. We managed to monitor colonization by Lanius of a glade clearing cut in 1979. Separate individuals of Nesting Time l. criswrus appeared there in 1980. Later, the over growing clearing became more and more suitable for In the zone where the two species are sympatric, Lanius nesting. In t 981, the number of L. cristatus dates of their arrival usually differ by 1-2 weeks: there was quite high and exceeded that of L. collurio Lanius collurio arrives in the middle of May, whereas 20 times, whereas the d.ensity on meadows with young, L. cristatus arrives at the end of May. As a rule, the rarefied , birch forest ·was equal for these species males arrive few days before the females. Occupation (Table I ). In 1982, the numbers of both species on the of territories and formation of pairs takes 1-1 .5 weeks. glade have become more similar, probably due to Nesting periods are quite extended and overlap, but in migration of L. collurio from meadows. the context of our work they are less important than Total number of both species of Lanius in the habi periods of pairing. tats desc ribed at the years of observations is shown in Table 2. At least half of all the noted pairs of L. collurio and only I of 11 pairs of L. cristatus were formed toward Figure 3 represents an example of spatial distribu the beginning of our observations near Kebezen' Vil tion of the both species on one of areas with fallen trees lage in 1978. From June 2 to 5, we observed the forma and forest margins edges near Kebezen' Village (see tion of three pairs of the first species and seven pairs of Kryukov, 1980). Here we can see centers of home the second. Therefore, there were I I pairs and nine sin ranges of territorial birds and sites where other birds · gle birds of L. cristatus compared to 20 pairs and 8 sin were encountered. Forty-eight L. collurio (20 pairs and gle birds in L. collurio. All these data indicate some 8 single birds) and 29 L. cristatus (I 0 and 9, respec shift in nesting times of both species, which is also con tively) were found in a 12.2-km stretch of free piles and finned for other sympatric localities. A certain propor forest margins. Mear. 'density of populations of the both tion of single males is retained further, forming a cer species, including non-nesting birds, composed 6.3 tain population reserve. After the arrival of l. cristatus, individuals per I km of a tran s~c t with mean pile width we repeatedly observed their occupation of territories of 22 m.