This paper deals with a large scale study of griffon vulture diet, based on a long-term GPS tacking program over 2 regions of Spain, using 55 individuals. The dataset consists in the identification of 4831 sites where vulture feeding events happened, including 3338 sites where the authors actually visited the place to determine what species was present. I salute this enormous field effort.
The results are very interesting and novel, built on solid methodology. The cultural transmission is really a new discovery in griffon vultures, with northern birds, more used to feed at large and predictable feeding sites, keep the same habit when travelling to the southwestern Spain, where they meet other birds from the South, who have different habits at less predictable feeding sites. This is fascinating.
The sex segregation in diet in griffon vultures was discovered only very recently by the same team (Fernández-Gómez, et al 2022. « Vultures Feeding on the Dark Side: Current Sanitary Regulations May Not Be Enough ». Bird Conservation International,), that I am surprised that this study is not cited. This sex segregation in diet found in vultures recalls me the example of giant petrels Macronectes spp, scavenging seabirds with many similarities with vultures, where there is also a strong sex segregation in diet, with males foraging more on beaches on seals and penguins while females forage more at sea. Several papers described this fact, among which:
Forero, et al 2005 « Stable Isotopes Reveal Trophic Segregation by Sex and Age in the Southern Giant Petrel in Two Different Food Webs ». Marine Ecology Progress Series 296: 107‑13.
González-Solís, et al (2007). « Offshore spatial segregation in giant petrels Macronectes spp.: differences between species, sexes and seasons ». Aquatic Conservation: Marine and Freshwater Ecosystems 17,: S22‑36.
González-Solís(2000). « Sexual dimorphism and sexual segregation in foraging strategies of northern giant petrels, Macronectes halli, during incubation ». Oikos 90: 390‑98.
The interesting thing is that in both cases, males chose the easy and predictable diets while females preferred less predictable food resources... Some authors hypothesized that the reason for such segregation in giant petrels would be sexual morphological dimorphism, with males being larger and dominant at carcasses, hence chasing females away from the most competitive foraging places (shores). Another interesting example (to my knowledge the only one in vultures) of sex segregation in foraging behaviour is the case of Andean condors, with males being larger than females, dominating them and leading females to forage in other habitats and at different times than males (Alarcon, etal 2017. « Sexual-size dimorphism modulates the trade-off between exploiting food and wind resources in a large avian scavenger ». Scientific Reports 7: 11461).
Yet in griffon vultures, sexual dimorphism is very small, and females are marginally larger than males, yet no dominance hierarchy favours females (Bosè, & Sarrazin 2007. « Competitive behaviour and feeding rate in a reintroduced population of Griffon Vultures Gyps fulvus ». Ibis 149, : 490‑501. ). So why does this happens in this way in vultures? As the authors state at lines 302-304: why males would be more prone to fall into ecological traps than females? May be the authors have some hypotheses that they can discuss?
I only have a few minor comments
The main problem in the current submission is the reference list: it appears a complete mismatch between the citations and the reference list. This may be due to the ref 18, that includes 2 references in the list: Moleon et al 2021 and Stephens&Krebs; 1986: I think that Stephens & Krebs should be ref 20... so I guess this is the reason for the subsequent mismatch. Please correct this
Minor comments
Line 83 and 100: Gyps in italics and capital letter
Line 267: sentence unclear: I guess a word is missing? Co-occurences?