Statistics of Swallow Nest Boxes at Buttertubs West Marsh in 2026.
Number of boxes: 30
Number of boxes with eggs: 28 (93%)
Number of eggs laid: 143
Mean clutch size (range): 4.9 (2-7)
Number of eggs hatched (% eggs hatched): 103 (72%)
Number of nestlings banded (% nestlings banded): 69 (67%)
Number of females banded: 17
Number of males banded: 2
Number fledged (% nestlings fledged): 40 (39%)
% eggs to fledglings: 28%
Fledging rate (young per pair): 1.4
Summary statistics of Tree Swallow nesting productivity at Buttertubs West Marsh during 2022-2026, and 13-year average.
| Parameter | 2022 | 2023 | 2024 | 2025 | 2026 | 14-year Average |
| Number of boxes | 36 | 36 | 30 | 30 | 30 | — |
| Number of boxes with eggs (% of boxes with eggs) | 20 (56%) | 24 (67%) | 25 (83%) | 25 (83%) | 28 (93%) | 22 (70%) |
| Number of eggs laid | 131 | 138 | 154 | 139 | 143 | 130 |
| Mean clutch size (range) | 5.7 (2-7) | 5.3 (3-6) | 5.5 (2-7) | 5.1 (2-7) | 4.9 (2-7) | 5.1 |
| Number of eggs hatched (% eggs hatched) | 116 (89%) | 120 (87%) | 104 (68%) | 124 (89%) | 103 (72%) | 97 (74%) |
| Number of nestlings banded (% nestlings banded) | 115 (99%) | 97 (81%) | 82 (79%) | 114 (92%) | 69 (67%) | 81 (83%) |
| Number fledged (% nestlings fledged) | 102 (88%) | 83 (69%) | 62 (60%) | 106 (85%) | 40 (39%) | 62 (65%) |
| % eggs to fledglings | 78% | 60% | 40% | 85% | 28% | 49% |
| Fledging rate (young per pair) | 4.4 | 3.2 | 2.2 | 3.9 | 1.4 | 2.5 |
