Evidence that helping at the nest does not result in territory inheritancein the Seychelles warbler

In an environment that has a shortage of territories, helping to rear young er siblings ('alloparenting') is proposed to facilitate territory acquisiti on in two ways: (i) through group augmentation that leads to an increase of the territory with subsequent partial inheritance (budding); and (ii) thro ugh site dominance that leads to greater success when competing for the nat al or a nearby territory after the death of the territory owner (complete t erritory inheritance), Most young Seychelles warbler (Acrocephalus sechelle nsis) mates either show alloparenting or budding behaviour. Future budders had significantly more aggressive interactions with neighbours and assisted their parents more with territory defence than similarly aged future allop arents or non-helpers. This led to an increase of the natal territory of fu ture budders before actual budding took place, whereas the natal territorie s of future alloparents remained constant in size. Alloparents never became budders and vice versa, refuting partial inheritance as an advantage of al loparenting. Natural male breeding vacancies were never inherited by allopa rents born on vacant or other territories, but were inherited by budders bo rn on the vacant territory or, if these were absent, predominantly by budde rs from neighbouring territories. We offer explicit experimental evidence a gainst the 'helping at the nest to inherit' hypothesis. Experimentally crea ted male breeding vacancies, with both a male alloparent and a similarly ag ed sibling budder present simultaneously in the vacant territory, were fill ed by budders only. Site dominance over territory inheritance is linked to budding and not to alloparenting.