Order of disposition, Family Court, New York County (Jeffry Gallet, J.), entered on or about September 14, 1993, terminating appellant’s parental rights and awarding guardianship and custody of the subject child to the Commissioner of Social Services and *328petitioner agency for the purposes of adoption, following a fact-finding determination that appellant had abandoned the child, unanimously affirmed, without costs.
The only excuse offered by appellant for his admitted failure to maintain contact with the child for the six-month period immediately prior to the filing of the petition (Social Services Law § 384-b [4] [b]) was his incarceration, which does not avail since it fails to explain why contact was not maintained through cards, letters or telephone calls (Matter of Anthony M., 195 AD2d 315, 316). Nor was the agency under a duty to encourage communication between appellant and the child during the abandonment period (Matter of Julius P., 63 NY2d 477, 481). The agency proved at the dispositional hearing, by a preponderance of the evidence, which is the applicable test (Matter of Celeste M., 180 AD2d 437, 438), that the child’s best interests required the transfer of custody and guardianship to the agency for the purposes of adoption by the foster mother, who has nurtured the child for almost her entire life, the only alternative offered by appellant being return of the child to the biological mother, who did not appear in the proceeding and has been indifferent to the defense of her own parental rights. Concur—Sullivan, J. P., Rosenberger, Wallach, Nardelli and Williams, JJ.