Several authors have described various aspects of the nest of the Bell Vireo, notably Goss (1891:535); Simmons (_in_ Bent, 1950:256), Nice (1929:13) and Nolan (1960:230-231). I can add but little to these descriptions. The nest itself is a compact structure composed of strips of bark and strands of grasses that are interwoven and tightly bound with animal silk. The floor of the cup is first lined with a layer of small leaves and then the entire interior is lined with fine stems or strips of bark. Feathers are occasionally used to pad the bottom prior to lining, as are pieces of wool and milkweed down. Nest 2-e (1960) had been packed with small pieces of soil bearing moss prior to lining. TABLE 6. ABORTIVE NESTING ATTEMPTS IN MAY AND JUNE OF 1960. ================================================== Nest | Length | Cause of abandonment | of time | | worked on | -----+-----------+-------------------------------- 1-a | 1 day | Heavy rain 1-h | 2 days | Female failed to build 2-a | 1/2 day | Female failed to build 2-c | 1 day | Protracted territorial dispute 4-a | 1 day | Female failed to build 5-a | 1 day | Female failed to build 6-c | 1 day | Heavy rain 7-a | 2 days | Female failed to build -----+-----------+-------------------------------- Early nests tend to be bulkier, having thicker walls and bottoms than later efforts. However, nests in May were found to have 16 per cent thicker bottoms and 41 per cent thicker walls than nests in June (Table 7). Standard nest measurements do not show this to be so, for the exterior and interior diameters at the rim are governed by the angle between the two branches of the fork. TABLE 7. DIMENSIONS OF NESTS IN MAY (1960) AND JUNE (1960). ======================================================== Measurements | May (N 10) | June (N 8) ------------------------+---------------+--------------- External depth | 61.6 mm. | 59.3 mm. Depth of cup | 45.5 mm. | 46.3 mm. Outside diameter | 57.3/55.5 mm. | 54.3/53.5 mm. Inside diameter | 43.4/42.2 mm. | 45.5/43.9 mm. Thickness of forward | | wall 1 inch below rim | 13.8 mm. | 7.6 mm. Thickness of bottom | 11.3 mm. | 4.6 mm. ------------------------+---------------+--------------- EGGLAYING AND INCUBATION _Egglaying_