a string of ducks Context-dependent Subjectduck (ducks)CategoryAnimals → BirdsContextin flightConfidencehighAttestationwikipedia-cited 2 sourcesWikipedia - List of animal namesOxford University Press - AskOxford: D
a string of horses Context-dependent Subjecthorse (horses)CategoryAnimals → MammalsContextponiesConfidencehighAttestationwikipedia-cited, wiktionary-attested 4 sourcesWikipedia - List of animal namesU.S. Geological Survey Northern Prairie Wildlife Research Center - Common Questions: What Do You Call a Group of...?Wiktionary - stringWiktionary - Appendix:English collective nouns