Garden Warbler. Blackcap. Whitethroat. Lesser Whitethroat. Redstart. Black Redstart. Robin. Reed Warbler. Sedge Warbler. Marsh Warbler. Grasshopper Warbler. Willow Wren. Hedge Sparrow. Common Wren. Whinchat. White Wagtail. Grey-headed Wagtail. Tawny Pipit. Meadow Pipit. Skylark. Yellowhammer. To this list Dr. Baldamus, from other sources, has added the following:[98]— Red-backed Shrike. Barred Warbler. Nightingale. Icterine Warbler. Chiff-chaff. Great Reed Warbler. Sedge Warbler. Fire-crested Wren. Tree Pipit. Crested Lark. Wood Lark. Common Bunting. Black-headed Bunting. Greenfinch. Linnet. Russet Wheatear. And lastly, in a foot-note to Mr. Dawson Rowley’s article on the Cuckoo,[99] in which the above lists were quoted, Professor Newton has pointed out the authority which exists for including the following, at least occasionally, amongst the foster parents of the young Cuckoo:— House Sparrow. Blue-throated Warbler. Rock Pipit. Chaffinch. Blackbird. Grasshopper Warbler.[100] Great Titmouse. Red-throated Pipit. Mealy Redpoll. Bullfinch. Jay. Song Thrush. Magpie. Turtle Dove. Wood Pigeon. He confirms, moreover, Mr. Rowley’s remark that the Cuckoo’s egg is occasionally found in the nest of the Brambling (_Fringilla montifringilla_). I have still to name four species which are not included in any of the above lists, _viz._, the Spotted Flycatcher, Yellow Wagtail, Grey Wagtail, and Wheatear. They were noticed by me some years ago in the first work I ever published.[101] In the case of the Wheatear, a nest of that bird containing three eggs of the Wheatear and one of the Cuckoo was placed under a clod, and in such a position as strongly to favour the opinion of some naturalists that the Cuckoo first lays her eggs and then deposits them with her bill in the nest. Considering the amount of attention which has been bestowed upon the Cuckoo by naturalists in every age down to the present, one would suppose that every fact in connection with its life-history was now pretty generally known. Such, however, is not the case. There are still certain points which require investigation, and which, owing chiefly to the vagrant habits of the bird, are not easily determined. How can it be ascertained with certainty, for example, whether the same hen Cuckoo always lays eggs of the same colour, or whether (admitting this to be the case) she invariably lays in the nest of the same species—that is, in the nest of that species whose eggs most nearly approximate in colour to her own?