May 4th.—Camp in mid-marisma. All this night, commencing about 10 P.M., a stream of migrating birds kept passing overhead. From the dark sky resounded for hours the cries of gulls and terns, sundry small land-birds, whimbrels, plovers and sandpipers of various species: besides harsher shrieks and notes that resembled those of hawks and herons of some kind.
Amidst such wealth of bird-life lies work for many spring-visits. The nesting-season, moreover (the most interesting period to the ornithologist), extends over a greater period of time than is the case at home. In Spain, with its early spring and warm equable climate, it might be supposed that most birds would nest both early and more or less simultaneously. But this is not the case. The period of reproduction, with birds, appears to be prolonged proportionately as one approaches the equator. In the far north, where summer is short and sharply defined, this period is the same. Thus in the arctic lands of Spitsbergen and Novaya Zemlya, it is limited to six weeks, and in Lapland and Siberia to two months or so, extending in Central Europe, roughly speaking, to three. In Andalucia domestic duties last, with one species or another, over half the year. There are cases in which nidification commences before Christmas—as with the Lammergeyer, Bonelli's Eagle, and the Eagle-Owl: the Griffon Vultures and some others are only a little later. Whereas, on the other hand, some of the herons do not nest till June: Ædon galactodes and the Little Bustard are still incubating in July, and the Flamingoes breed so late that their young can hardly be on the wing before the latter month.
Among the earlier breeders is the Spanish Green Woodpecker, which drills deep holes in the hard wood of cork-oak or olive, and lays six shining white eggs in March. Now (April) they had young, but rear a second brood in May. Though they are so abundant, yet the "tapping" sound characteristic of the Woodpeckers is not heard in the Spanish forests, for their food consists of ants and of the small, red and black beetles that cluster in every crevice of the rough cork-bark.
The Rollers were also laying in mid-April—here in hollow trees, elsewhere in crevices of rocks or ruins: but wherever their treasure may be, the silly birds are sure to disclose its position by their incessant "caterwauling," and anxious, tumbling flight. On the 17th April we found the first nest of the Southern Grey Shrike (Lanius meridionalis) in a high mastic-bush. The nest resembled that of the Missel-Thrush, the five eggs larger and more darkly marbled than those of the northern L. excubitor. Nests of the Woodchat (L. rufus) may be found in almost every bush from May 10th onward, and the Bee-eaters have then formed swarming colonies in the river-banks like Sand-Martins.
As remarkable a freak as any in nature is the system of reproduction by proxy adopted by the Great Spotted Cuckoo (Coccystes glandarius). This smart and handsome bird, though more abundant in Estremadura and the Castiles, is fairly numerous on the wooded prairies of Andalucia, where its curious nesting habits may be observed with ease. The parasitic habits of the European Cuculidæ are well known—none of these birds building a nest or rearing their own young. Our British Cuckoo deposits its eggs singly in the nests of hedge-sparrow, warbler, wagtail, or other small bird—it is not particular which. The Spotted Cuckoo, however, does not impose this duty of rearing her young upon her neighbours generally, but almost exclusively upon the common Magpie: though exceptionally upon the Azure-winged species (Cyanopica cookii) and the Raven as well. At the Encinar del Visco, during the past year (1891), the writer found two of the Cuckoo's eggs in a nest of that bird, along with three eggs (one broken) of the owner.[54]
The Spotted Cuckoo, moreover, lays eggs so exactly resembling those of the selected foster-mother (the Magpie) as to be hardly distinguishable. On close examination, it is true, they do differ in their more ellipitic form and granular surface: but, unless previously aware and specially on the look-out, no one, probably, would suspect they were not Magpie's eggs—apparently not even that cute bird itself does so. Even so experienced an ornithologist as Canon Tristram failed to discriminate the difference—this was in Algeria—till the zygo-dactylic foot of the embryos betrayed the secret (Ibis, 1859).
The Spotted Cuckoo deposits two, three, and even four eggs in the same Magpie's nest—sometimes leaving the original owner's eggs undisturbed, in other cases removing all or part of them: we have noticed spilt yolk and the shells of broken eggs at the entrance to the nest and on the branches below. Hatched thus, in the domed and enclosed nests of the Magpie, it seems difficult for the young Spotted Cuckoos to eject their pseudo-brothers and sisters; but we cannot speak definitely as to this detail in the early life-history of these curious usurpers of hearth and home.
The only egg of the Common Cuckoo we have ever found in Spain was in a nest of the Stonechat. This was on April 23rd, and there were four eggs of the Stonechat. The Cuckoo is common in Spain on passage, arriving early in April; a few remain to breed, and we have heard their note up to the end of May, but the majority pass on northwards at once.
The Azure-winged Magpie, above referred to, is very local in the south. It nests not far from Jerez, and in some numbers near Coria del Rio, but is much more abundant in the wooded vegas of Cordova, and still more so in Estremadura and Castile, actually swarming near Talavera de la Reyna, at Aranjuez, etc. Their nests, placed on bushes rather than trees, resemble a Jay's, slightly built of sticks exteriorly, and completed with green moss, dry grass, etc., and contain five or six eggs. Half-a-dozen nests may often be found within a hundred yards. An active, sprightly bird, exclusively confined to the Spanish Peninsula.
