Certhia Brachydactyla Research Articles

Utilisation de l’espace par deux espèces jumelles Certhia brachydactyla et familiaris en zone de sympatrie

The use of space by two sibling species of passerines, the Treee creeper, Certhia familiaris and the Short-toed Tree creeper C. brachydactyla was studied in the Alpes-Maritimes, Southern France. The two species were found differ mainly by their altitudinal distribution, the Short-toed Tree Creeper living at low altitudes, and the Tree creeper occuring at higher elevations. This replacement took place gradually, and an important area of sympatry was found between 1200 and 1800 m above sea level. In this altitudinal belt each species had a definite preference for a few tree species (the Tree creeper for Spruce Picea excelsa and Fir Abies alba, and the Short-toed Tree creeper for Scots pine Pinus silvestris), as well as for a different kind of forest (the Tree creeper prefering dense stands, and the Short-toed Tree creeper more open ones). In Larch Larix decidua forests at middle altitudes, however, the two Tree creepers were found to occur at similar densities and were syntopic. In such Larch woods, a large overlap of foraging sites (substrate, foraging height, and foraging posture) was observed throughout the year. No interspecific territoriality was noticed during the breeding season, and the two species displayed few interspecific reactions to song playback. Interspecific agonistic behaviour was observed at four occasions only. Therefore, these two morphologically very similar species did not show any evidence of competition during their reproductive season in Larch woods. Some spatial segregation did, however, occur in winter, when the Tree creepers joined flocks of tits, in which the two species were seldom seen together.

Experiments on the origin of dialects in the short-toed tree creeper (Certhia brachydactyla)

Wild short-toed tree creepers in southern Germany were exposed to tape recordings of seven song types from other dialects or song institutions and sixteen song types from thirteen handreared Middle European birds. One song type from southern Germany was used as a control. The males reacted strongly to two slightly different Spaish dialects and not at all or only feebly to one song institution from Cyprus and four from Morocco. The song types of the hand-reared birds had less effect than controls. The songs of two birds from southern Germany hand-raised together were quite similar to those from Cyprus. We conclude that Cyprus and North Africa on the outskirts of the species distribution were colonized by short-toed tree creepers who had had no opportunity to learn their songs from adult conspecifics.

Feeding Niches of Woodland Birds in a Montane Coniferous Forest in Central Spain during Winter

A short-term study of the feeding niche differentiation of some passerine birds was conducted in a montane pine forest in central Spain during one winter, and the results were compared with similar data from northern Europe. Only six species of passerines were fairly common in the study area. The distribution of densities seemed to be more even than in northern Europe. The so called pariform guild as defined in Scandinavian studies, was found to consist of three distinct groups of species according to their foraging patterns: a group of generalized ground, shrub and branch foragers, another of specialized foliage foragers and a third of specialized trunk foragers. The last group overlaps so little with the rest of the species, that it should be excluded from the guild. Parus montanus and Certhia familiaris are not found in central Spain, while they are common in northern Europe. Instead Sitta europaea and Certhia brachydactyla were relatively common. The higher average temperatures for the winter months in central Spain when compared with northern Europe may induce a greater resource abundance, which possibly explains the broader niche of Parus cristatus and the abundance of Sitta europaea. No major effects on the foraging patterns of Parus cristatus and Parus ater by the absence of Parus montanus were observed, but the distribution of P. cristatus in the pines may be affected by the presence of Sitta europaea.

Ritualized distinctiveness of song in closely related sympatric species

There are so-called sibling species in all groups of animals. Sibling species are species, which are very similar in appearance, they inhabit the same area, but they do not pair. Let us take, for example, our two Tree Creepers, the Short-toed Tree Creeper and the Tree Creeper. Only specialists are able to distinguish these two species in the field without hearing them singing or calling. But the songs of the two species differ in quite a striking manner (figure 1).

Climatic Adaptation in Some Small Northern Birds

Large northern mammals like the eskimo dog or the arctic fox are provided with such good insulation that their thermoneutral zone may extend as far down as the temperature of the coldest winter night. They enjoy a complete insulative adaptation to cold (Scholander, Walters, Hock, and Irving 1950a; Scholander, Hock, Walters, Johnson, and Irving 1950b; Scholander, Hock, Walters, and Irving 1950c; Scholander, Lange Andersen, Krog, Vogt Lorentzen, and Steen 1957). If we consider the smaller animals living in the same climate, however, we find that the insulation dwindles with decreasing size, in some cases down to values no greater than those we find in tropical animals (Palmgren 1944, Scholander et al. 1950a, Irving, Krog, and Monson 1955). The northern species do not have an elevated basal heat production compared to their tropical relatives and as a consequence their critical temperature is well above zero, as for example +20'C for red squirrel, +15'C for lemming, +20'C for wild Norway rat and + 100C for snow bunting. All of these were measured in arctic Alaska in the wintertime. Whenever the environment goes below the critical temperature, the animals must increase their inetabolic rate to maintain their body temperature. This situation prevails most of the wintertime. The extra heat may readily be supplied in the daytime by locomotor and other activities of the animal. The question is, however, what happens during the night time when the animal is at rest and asleep and the temperature is even lower than in the day ? To meet this situation most small mammals and some birds avoid the cold night by seeking shelter. Ptarmigans and snow buntings dig down under the snow on cold nights. Chickadees spend the night in hollow trees, bird-boxes and similar places, but many small birds evidently spend the night in the open. Huddling is a common occurrence in small mammals such as mice (Sealander 1952). L6hrl (1955) describes treecreepers (Certhia brachydactyla) gathering into tight bunches of 10-20 individuals during cold nights. When rats are exposed to cold stress for a long time they develop a significant metabolic acclimation to cold (Hart 1957). This increased