What kinds of studies are most needed to understand the effects of global change on nature? Two deficiencies stand out: lack of long-term studies  and lack of data on species interactions . The paper by Mennerat and colleagues  is particularly valuable because it addresses both of these shortcomings. The first one is obvious. Our understanding of the impact of climate on biota improves with longer times series of observations. Mennerat et al.  analysed an impressive 18-year series from multiple sites to search for trends in parasitism rates across a range of temperatures. The second deficiency (lack of species interaction data) is perhaps not yet fully appreciated, despite studies pointing this out ten years ago [2,4]. The focus is often on species range limits and how taking species interactions into account changes species range predictions based on climate alone (climate envelope models; ). But range limits are not everything, as the function of a species (or community, network, etc.) ultimately depends on the strengths of species interactions and not only on the presence or absence of a given species [2,4]. Mennerat et al.  show that in the case of birds and their nest parasites, it is the strength of the interaction that has changed, while the species involved stayed the same. Mennerat et al.  found nest parasitism to increase with temperature at the nestling stage. They have also searched for trends of parasitism dynamics dependence on the host, but did not find any, probably because the nest parasites are generalists and attack other bird species within the study sites. This study thus draws attention to wider networks of interacting species, and we urgently need more data to predict how interaction networks will rewire with progressing environmental change [6,7].
 Lindenmayer, D.B., Likens, G.E., Andersen, A., Bowman, D., Bull, C.M., Burns, E., et al. (2012). Value of long-term ecological studies. Austral Ecology, 37(7), 745–57. doi: 10.1111/j.1442-9993.2011.02351.x
 Tylianakis, J.M., Didham, R.K., Bascompte, J. & Wardle, D.A. (2008). Global change and species interactions in terrestrial ecosystems. Ecology Letters, 11(12), 1351–63. doi: 10.1111/j.1461-0248.2008.01250.x
 Mennerat, A., Charmantier, A., Hurtrez-Bousses, S., Perret, P. & Lambrechts, M.M. (2019). Parasite intensity is driven by temperature in a wild bird. bioRxiv, 323311. Ver. 4 peer-reviewed and recommended by PCI Ecology. doi: 10.1101/323311
 Gilman, S.E., Urban, M.C., Tewksbury, J., Gilchrist, G.W. & Holt, R.D. (2010). A framework for community interactions under climate change. Trends in Ecology & Evolution, 25(6), 325–31. doi: 10.1016/j.tree.2010.03.002
 Louthan, A.M., Doak, D.F. & Angert, A.L. (2015). Where and when do species interactions set range limits? Trends in Ecology & Evolution, 30(12), 780–92. doi: 10.1016/j.tree.2015.09.011
 Bartley, T.J., McCann, K.S., Bieg, C., Cazelles, K., Granados, M., Guzzo, M.M., et al. (2019). Food web rewiring in a changing world. Nature Ecology & Evolution, 3(3), 345–54. doi: 10.1038/s41559-018-0772-3
 Staniczenko, P.P.A., Lewis, O.T., Jones, N.S. & Reed-Tsochas, F. (2010). Structural dynamics and robustness of food webs. Ecology Letters, 13(7), 891–9. doi: 10.1111/j.1461-0248.2010.01485.x
The authors have revised the manuscript according to the comments of the reviewers and myself which has improved the manuscript and it is now almost ready for recommendation. Before I recommend the manuscript, I would like the authors to correct a typo which I found during my last reading (incorrect use of "however" on line 281) and to publicly deposit the data on which this manuscript is based according to PCI rules.
First, I would like to apologize for how long it took me to make the decision – it was difficult to get reviewers in the summer. After considering two reviews and my own reading of the manuscript I ask you to revise the manuscript. Both the reviewers and I think that it would be a valuable contribution if you address the comments. I especially appreciate the temporal scale of the data and the strength of the evidence which comes with it. Currently the manuscript is narrowly focused on temperature effect on the parasites. In addition to reviewer comments, I would like you to explicitly consider aspects of host-parasite dynamics in the manuscript in addition to temperature. Could you test if there is evidence for dependence of the parasite population on performance or population size of the host in previous year, or in some other way relate parasitoid dynamics to host dynamics?