habían anillado
Past perfectellos/ellas/ustedesconjugation ofanillar.

anillar

De hecho, el año pasado tuvimos otra recaptura asombrosa de un Catharus minimus que investigadores de SELVA habían anillado en Belice durante la primavera del 2008 y que luego recapturaron en Colombia en el 2014.
Indeed, last year we had an even more remarkable recapture of a Gray-cheeked Thrush that had been banded by SELVA researchers in Belize during the spring of 2008 and was recaptured by the same researchers in Colombia in April 2014.
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