The bird count rise from 2000–2009 to 2015–2025 did not restore the 1969–1978 species mix on one Hubbard Brook plot

We tested whether a later rise in adult bird counts restored the early species mix on one 10-hectare plot at Hubbard Brook, New Hampshire. We used all 33 species in EDI release knb-lter-hbr.81.9. Mean counts were 184.38 adults per 10 ha in 1969–1978, 92.95 in 2000–2009, and 119.20 in 2015–2025. The last period has ten observed seasons; 2020 has no data. The later rise was 28.2%, but it recovered only 28.7% of the early total loss. We split that rise by each species’ early mean. Smaller deficits supplied 6.13 adults per 10 ha. Growth in counts above early means supplied 20.13, or 76.7% of the net rise (95% conditional resampling interval 56.3% to 95.9%). Total variation distance between species shares and the early mix changed from 0.479 to 0.499. Its change was +0.020 (95% interval −0.002 to +0.039). The interval does not resolve a small distance increase. A planned Hellinger distance check gave an increase of 0.050 (0.027 to 0.071). Trace-value and year-window checks kept the whole-list point change positive. A nine-species subset with no trace records gave an uncertain negative change. The full-list rise therefore did little to restore the early species mix. This result is local. The intervals use joint year vectors in short time blocks and do not include systematic census error. The package has the source data, provenance, code, all results, figures, and a verified offline repeat. We do not infer causes or claim that the distinction between total count and composition is new.

bird community · Hubbard Brook · species composition · ecological recovery · territory mapping · long-term monitoring · reproducible analysis