This study is a rare empirical study of dispersal distances and the correlates of natal dispersal in a North American migratory songbird—Wood Thrush. The authors estimated natal dispersal distances and the proportion of “long-distance” dispersers at 12 sites, and related that proportion to conspecific density and factors representing habitat quality. The authors do a great job of laying out the alternative hypotheses that might govern natal dispersal decisions. Their conclusions allow them to rule out random processes shaping dispersal patterns, and imply that the landscape attributes of their study region (i.e. habitat amount) are not important for explaining the movements of this species in this location. While I did not find the results particularly surprising, I agree with the authors when they argue that we have relatively few good empirical data sets with which to determine natal dispersal distances in birds, and therefore, we have limited opportunity to understand how dispersal works in mobile taxa. However, in this regard, I think the authors might consider including reference to some of other studies of avian natal dispersal—it isn’t quite so under-studied as lines 59-60 imply:
Anderson, K. E., M. Fujiwara, and S. I. Rothstein. 2012. Demography and dispersal of juvenile and adult Brown-headed Cowbirds (Molothrus ater) in the Eastern Sierra Nevada, California, estimated using multistate models. Auk 129:307-318. doi:10.1525/auk.2012.11163.
Fajardo, N., A. M. Strong, N. G. Perlut, and N. J. Buckley. 2009. Natal and breeding dispersal of Bobolinks (Dolichonyx oryzivorus) and Savannah Sparrows (Passerculus sandwichensis) in an agricultural landscape. Auk 126:310-318. doi:10.1525/auk.2009.07097.
Guerrini, M., C. Gennai, P. Panayides, A. Crabtree, I. Zuberogoitia, A. S. Copland, O. Babushkina, P. M. Politi, D. Giunchi, and F. Barbanera. 2014. Large-scale patterns of genetic variation in a female-biased dispersing passerine: the importance of sex-based analyses. PLOS One 9. doi:10.1371/journal.pone.0098574.
Haché, S., K. A. Hobson, E. M. Bayne, S. L. Van Wilgenburg, and M.-A. Villard. 2014. Tracking natal dispersal in a coastal population of a migratory songbird using feather stable isotope (δ2H, δ34S) tracers. PLOS One 9:e94437. doi:10.1371/journal.pone.0094437.
Hardouin, L. A., M. Nevoux, A. Robert, O. Gimenez, F. Lacroix, and Y. Hingrat. 2012. Determinants and costs of natal dispersal in a lekking species. Oikos 121:804-812. doi:10.1111/j.1600-0706.2012.20313.x.
McCaslin, H. M., T. T. Caughlin, and J. A. Heath. 2020. Long-distance natal dispersal is relatively frequent and correlated with environmental factors in a widespread raptor. Journal of Animal Ecology 89:2077-2088. doi:10.1111/1365-2656.13272.
Winkler, D. W., P. H. Wrege, P. E. Allen, T. L. Kast, P. Senesac, M. F. Wasson, and P. J. Sullivan. 2005. The natal dispersal of Tree Swallows in a continuous mainland environment. Journal of Animal Ecology 74:1080-1090.
Woltmann, S., T. W. Sherry, and B. R. Kreiser. 2012. A genetic approach to estimating natal dispersal distances and self-recruitment in resident rainforest birds. Journal of Avian Biology 43:33-42. doi:10.1111/j.1600-048X.2011.05572.x.

I appreciate that Ecology Letters imposes strict ms length limitations. However, there were many important pieces of information missing from this ms that impeded my ability to thoroughly assess the value of the contribution. I explain those in turn, below, and suggest that if there is not space in the main text, much of this could be added to the Supplementary material.

(1) I had to dig to find the sample size. Although the 12 sites were mentioned, the number of individual birds for which the authors estimated dispersal locations/distances was never mentioned in the text. I did find site-specific numbers in table 1 and in Appendix 2, they state the N was 502. While 12 is the sample size for tests of site-level correlates of dispersal, I would have liked to know a lot more about the dataset. Given that we know little of dispersal patterns, what did the dispersal assignments reveal about geographic patterns? On line 141, the authors state they had too little data to evaluate dispersal patterns by sex or by year. Perhaps within-sites this is true, but it seems plausible they could describe how dispersal patterns varied with respect to these variables in the whole data set.
(2) I would like to see some assurance that the authors intend to make the data available upon publication.
(3) Can we please see a map of the study area? The text states that all 12 sites are located in Southern Illinois. Is there really enough variation in stable isotope signature or wing length within this region to make robust inferences regarding dispersal origins? Can you provide evidence that the wing length patterns are evident in HY birds?
(4) Did you capture any banded birds that had dispersed among sites and if so, can you use these to check your assignment methods?
(5) Did you constrain geographic assignments using landcover classifications and knowledge of the species’ breeding habitat associations? Presumably such methods could help refine the spatial reliability.
(6) The results are quite sensitive to the priors. This would make me take a hard look at all the assumptions in the analysis framework. If I understand it correctly, although the authors present results from three different shape and size parameter combinations of the dispersal kernel prior, all three assume that short-distance dispersal should be the norm. In other words, they assume higher dispersal propensity to locations near to the natal sites and rarer long-distance dispersal. While I agree that this assumption for most taxa, is probably true, it conflicts with the earlier assertion that we have few unbiased datasets with which to determine the patterns of dispersal. Migratory birds are not a whole lot like most other taxa because they move a lot in between breeding seasons. So what is true for “most organisms” may well not be true for migrants (line 201). Through tracking technologies, we are gaining a better picture of the many movements birds make that defy traditional “migration” and “dispersal” labels (e.g. Brown, J. M., and P. D. Taylor. 2017. Migratory blackpoll warblers (Setophaga striata) make regional-scale movements that are not oriented toward their migratory goal during fall. Movement Ecology 5:15. doi:10.1186/s40462-017-0106-0.) Post-breeding prospecting and migration may well afford migrants a lot of opportunity to prospect and “disperse” over long distances at essentially zero cost because the dispersal movement happens in the context of returning from wintering areas. I would love to see the results of analyses that make different assumptions about the median dispersal distances.
(7) After estimating dispersal locations and distances at the individual level, I was disappointed to see that the richness in that dataset got collapsed down to a “long” and “short” dispersal categorization, and then each site was characterized based on the proportion of birds that dispersed in over these two scales. The long- and short categorization was not based on any biological rationale and ignored any other information the authors might have had regarding the scale or direct of travel. It seemed a great shame to collapse the richness of the individual dataset in this way. Perhaps this is why there was so much site-level uncertainty in the site-level estimates in figures 2 and 3 and the relatively weak statistical support for the conclusions? I am not quite sure what the solution is here, but I would encourage the authors to re-examine this particular analytical choice.

Many thanks for the careful responses and revisions to the manuscript. The authors addressed all my concerns with this revision.