FEET OF SWALLOWS. 257 



are among the most exclusively wing-birds, and the 

 best winged in the whole class. Their food is in 

 smaller portions than that of any others of the class, 

 and thus they have more labour in the procuring of 

 it. Not only this, but many of them have much 

 labour in the construction of their nests, whether they 

 build them of mortar in the crevices of rocks or the 

 apertures or angles of buildings, or excavate them in 

 the banks ; and all of them have much toil in the 

 rearing of their broods, which, as is general with 

 birds that have very perfect feathers, continue a long 

 time in the nest. 



Their feet more resemble the syndactylic ones 

 than those of any other form, though these have the 

 toes united, and consequently a narrow foot, while the 

 birds under consideration have one remarkably broad 

 for its length ; but they both agree in this, that the 

 tarsi and toes are short, and they use the feet only for 

 resting or holding-on, and rarely if ever for progressive 

 motion. It is worthy of remark, as a striking instance 

 of agreement in two very important habits, that though 

 the syndactylic birds build low, and the ones under 

 consideration build high (for even the sand-martins, ot 

 bank-swallows, build in lofty banks and rarely in low 

 ones), they should both have covered nests, and both 

 feed their broods for a long period, as well as both 

 capture their prey on the wing. And the height at 

 which they build corresponds to that at which they 

 fly. The kingfishers and bee-eaters never have 

 their nesting-hole far above the surface of the water ; 

 and their flight, when in search of food, is invariably 

 low. Of the swallow tribe, again, the sand-martin, 

 which builds in holes of the banks, is the bird of 

 lowest flight ; and the flight and position of the nest 

 rise together, till we come to the swift at the top of 



