According to our reference method, the point of emigration occurred over a wide window (39-250 dafterfledgingdging - method 12).
Methods 1-6 and 8-11 have been previously used but, as alluded to above, there are some potential problems with these methods identifying a point of emigration that does not fit the observed location pattern.
The variation between methods of estimating the point of emigration for golden eagles was substantial and reflects the high inter-individual variation in timing and complexity of behaviour during early life.
Despite the limitations of verification data, it is currently one of the only methods of measuring health professional emigration from Ireland.
This method assumes that the point of emigration at the start of dispersal is the most distinct movement away from the natal home range, thus the variation in distance (standard deviation) is largest compared to the mean distance from the nest at the point of emigration.
These two studies highlighted that there was a tendency to assign prematurely the point of emigration across these methods.
The tendency of these methods to prematurely assign the point of emigration due to pre-dispersal excursions has been noted in several other studies amongst other birds of prey [ 18, 20, 33].
The method used to calculate the point of emigration had a significant effect on the estimated values for each individual (Friedman rank sum test χ = 168.20, df = 11, p < 0.001).
The range of estimates of the point of emigration for all the methods, was 14 to 365 days after fledging, encompassing almost the entire period of our study (Table 2).
A total of 8% (283 of 3483) of locations were outside of the modelled natal home ranges, up to a maximum distance of 44 km from the natal nest prior to the point of emigration as estimated by method 12. Two individuals were never recorded outside of the natal home range prior to their estimated point of emigration.
Previously published methods provided very different estimates of the point of emigration with a general tendency for most to apparently assign it prematurely.
