76 The Food of Some British Wild Birds. 



which are, in addition, usually filled with small stones and sand. 

 Amongst these, some strip the fruits and seeds when they first lay 

 hold of them, and thereby condemn them to destruction. To this 

 group the following birds of those employed in the experiments 

 belong, viz., the turkey, the common fowl, the pigeon, the duck, 

 the cross-bill, the bullfinch, the goldfinch, the siskin, the serin-finch, 

 the nutcracker, and the titmouse. No seed, under ordinary condi- 

 tions, was found capable of germination, in the excrement of these 

 birds ; only when on a few occasions food was forcibly administered 

 to the fowl and to ducks, so that their crops must have been over- 

 loaded, were a few seeds found to have escaped pulverization, and to 

 still possess the power of development. The seeds used were those 

 of Arenaria serpyllifolia, Papaver rhaeas, Sisymbrwm sophia, Ribes 

 rubrum, Ligustrum vulgare, Fragaria indica, and other species. 



Ravens and jackdaws form a second group, in that the stones of 

 the drupes and hard-coated seeds of the berries which they ate 

 passed uninjured through the intestine, whilst soft-coated seeds and 

 fruits were all destroyed. Kerner emphasises the fact that after 

 these birds had been fed with cherries their excrements contained 

 cherry -stones 15 mm. in diameter, every one of which was able to 

 germinate. Of the birds selected for experiment, the blackbird, 

 the song-thrush, the rock-thrush, -and the robin formed the third 

 group. Of these the blackbird was the least fastidious about its 

 food. It even swallowed the fruits of the yew without afterwards 

 relieving its crop of the stony seeds, and it never rejected a single 

 fruit that was mixed with its food. The song-thrush refused all dry 

 fruits of 5 mm. in diameter or more, even when they were mixed 

 with the finely -chopped meat with which the bird was fed. They 

 also avoided certain strong-smelling fruits, such as that of the 

 yarrow. On the other hand the aromatic fruits of Umbelliferae 

 (e.g., Bupleurum rotundifolium and Carum carvi) were eaten with 

 great avidity. The seeds of the tobacco-plant, henbane, and fox- 

 glove mixed with the food were not rejected and caused no ill effects, 

 neither did the berries of the deadly nightshade, which were greedily 

 devoured. On the other hand, however, a song-thrush sickened after 

 eating berries of Phytolacea. When fleshly fruite with seeds of 

 diameter exceeding 5mm., such as those of Berbers, Ligustrum, 

 Opuntia, and Viburnum were introduced into the crop, the pulp 

 passed into the gizzard, but all the seeds were thrown up. Many 

 seeds, as, for example, those of J^ychnis flos-jovis, were carefully 

 removed from the rest of the food with which they had been mixed. 

 The seeds of fleshy fruits which were greedily devoured were thrown 

 out of the crop if the stones which they enclosed measured as much 

 as 3 mm. 



The interval of time between ingestion and evacuation in those 

 species belonging to the third group was surprisingly short. A 



