Breeding schedule.—Sixty records of breeding span the period May 11 to June 20 ([Fig. 6]); the modal date for completion of clutches is June 5.
Nearly 75 per cent of all clutches are laid in the period May 21 to June 10. Under unusual circumstances time of breeding can be greatly delayed; such circumstances occurred in 1961 in many places along the Kansas River in eastern Kansas, where the soft, sandy-clay banks were repeatedly washed away in May and June by high water undercutting the cliffs. Bank Swallows attempted to work on burrows in late May, but stabilization of the banks occurred only by late June, and the peak of egg-laying for many colonies was around July 12. Records for 1961 are omitted from the sample used here ([Fig. 6]).
Number of eggs.—Clutch-size is 5 eggs (4.8, 3-7; 60). Yearly clutch-size at one colony 3 miles east of Lawrence, Douglas County, is as follows:
| 1959: | 5.2, 19 records |
| 1960: | 5.0, 12 records |
| 1961: | 3.7, 11 records |
| 1962: | 4.8, 18 records |
The sample for 1961 is that taken in early July when breeding occurred after a delay of more than a month, as described above.
Nesting chambers are excavated in sandy-clay banks, piles of sand, piles of sawdust, or similar sites, at ends of tunnels one to more than three feet in depth from the vertical face of the substrate.
Rough-winged Swallow: Stelgidopteryx ruficollis serripennis (Audubon).—This summer resident is common in most places; it is not restricted to a single habitat, but needs some sort of earthen or other substrate with ready-made burrows for nesting. Temporal occurrence is indicated in [Table 14].
Breeding schedule.—The 14 records of breeding are in the period May 11 to June 30; the modal date of egg-laying is June 5. Seventy per cent of all eggs are laid in the period May 21 to June 10.
Number of eggs.—Clutch-size is 5 eggs (5.0, 4-6; 4).
Nesting chambers are in old burrows of Bank Swallows, Kingfishers, rodents, or in crevices remaining subsequent to decomposition of roots of plants; frequently this swallow uses a side chamber off the main tunnel, near the mouth, of a burrow abandoned or still in use by the other species mentioned above.