Russian Olive (Elaeagnus angustifolia) Dispersal by European Starlings (Sturnus vulgaris)

Ryan J. Edwards, Larry C. Clark, and K. George Beck (2014) Russian Olive (Elaeagnus angustifolia) Dispersal by European Starlings (Sturnus vulgaris). Invasive Plant Science and Management: July-September 2014, Vol. 7, No. 3, pp. 425-431. doi: http://dx.doi.org/10.1614/IPSM-D-13-00082.1

Abstract

Studies were conducted to document that European starlings consume Russian olive fruits and determine subsequent effects on seed germination. In the first study, avian feeding patterns at Russian olive trees were monitored over a 1-yr period using motion activated digital photography. Starlings fed on Russian olive fruits with highest activity occurring in November and December. In a second study, 20 captive European starlings were fed Russian olive fruits and seed germination rates were determined for three categories: consumed by starlings, hulled fruits (pericarp removed), and whole fruits. Starlings readily consumed Russian olive fruits and most seeds were regurgitated 30 min after consumption. Germination rates of ingested/regurgitated seeds (57%) and pericarp-removed seeds (40%) were greater than whole fruits (0%). Viability tests confirmed that 85% of starling ingested seeds remained viable after consumption. Our data suggest that Russian olive dispersal may be dependent upon animals for effective spread.

Nomenclature: Russian olive, Elaeagnus angustifolia L., European starlings, Sturnus vulgaris.

Management Implications: Our research clearly demonstrates that European starlings will consume Russian olive fruits. Most consumed seeds would be regurgitated and left on the soil surface in a more germinable state than whole fruits. This strongly suggests that Russian olive is dependent upon animals to disperse seeds and cause spread of this invasive species. Russian olive fruits are palatable to European starlings and many other bird and several mammal species that contribute to its effective spread. The change in germinability in fruits consumed by European starlings provides impetus for managing Russian olive particularly if passage through other animals' GI tracts has a similar effect. This interaction between two invasive species likely will change our collective impressions of their management importance.