Audouin’s Gull Colony Itinerancy: Breeding Districts as Units for Monitoring and Conservation

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I have completed my review of ‘Colony Itinerancy and Population Management: Insights from Audouin’s Gull (Ichthyaetus audouinii) in a Key Area of its Breeding Range,’ which is currently under consideration for publication in Diversity. The authors investigated the spatial structure and local survival of Audouin’s gull (Ichthyaetus audouinii) adult breeders across multiple breeding sites in the central Mediterranean Sea. They identified two strategies: adults who tended to be site-faithful and those who moved between different units. Gulls often change breeding sites at smaller levels (sub-colony and colony) without incurring a survival cost. In contrast, adult dispersal at a larger level (district) is uncommon and comes with a cost to survivorship, particularly for movers. I enjoyed reading the manuscript and believe it could be essential to understand the population dynamics of a critical species in the Mediterranean Sea. However, the manuscript has some issues that need further clarification.

 

1. The authors must confirm that all individuals were banded as chicks or specify the proportion of adults included in the analyses. Adults banded as chicks should show a different capture-recapture history. These individuals should be over two years old or even older. At what age do they start breeding? Additionally, among the 750 adult breeders in the study, please specify the proportion of site-faithful and mobile individuals by district or region.

 

2. Ideally, the authors should explain the likelihood of site and awareness changes. In the survival analyses (Table 1), age had an additive effect on local survival (phi) at both the colony and basin levels. Additionally, time had an additive effect on awareness change at all levels. It would be helpful if the authors could discuss these results in greater detail.

 

3. The authors describe two strategies (site-faithful vs. movers) with different local survival rates. Are there other differences in life history between these strategies? In other seabird species, it is common to observe varying strategies with distinct life histories (see Velarde and Ezcurra 2018 DOI: 10.1650/CONDOR-17-5.1, de la Cruz-Pino et al. 2024 https://doi.org/10.3354/meps14311). Understanding these life history differences may assist in improving the monitoring and population management of the species. 

 

4. It would be helpful to include the names of districts, regions, and basins in Figures 2, 3, and 7. If possible, please standardize the colors. 

 

5. In this version, the supplementary material only includes the figures. The various appendices are absent.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The study is well designed and provides an insightful assessment of survival in relation to the spatial scale of distribution for this vulnerable species. The results are clear-cut and highlight the potential risks associated with dispersal and movement. Given the ongoing decline of the species in the Mediterranean and its erratic breeding behavior, colony instability appears to be a critical factor affecting long-term survival. In this context, the conservation implications of the study are highly significant and offer valuable guidance for future management efforts. The study is worth publishing. I have some commetns that might improve the manuscript for the readers:

 

In the Methods section:

1) The spatial distinctions of the breeding distribution of the species is mostly welcomed in the absence of relevant common terms in the existing literature. I would suggest sub-colony level= breeding nuclei, Colony = Colony (it remains as it is), District level= Colony complex or Colony Cluster, Region level= Region level (it remains as it is) and Basin level = Zone level (because this refers to large areas with similar eco-geographical features).

2). It is not self-evident to all readers that “trap-aware” is a proxy for behavioral response to prior detection. I would suggest to clearly define the Markovian states as modeling behavioral response to previous detection (trap dependence).

3) If I have understood correctly the younger individuals are more likely to leave the breeding site implying that they exhibit low site fidelity and are more prone to dispersal. This movement can take the form of permanent emigration, where an individual leaves the study area and never returns, or temporary emigration, where it skips one or more breeding seasons but may return later. In capture–recapture terminology, transient individuals (as those used in U-CARE) are an excess of individuals that are observed only once and never resighted again. This pattern can result from true mortality, permanent emigration, or temporary emigration combined with detection failure. Can you clarify if the GOF test detected transience, as this could produce an underestimate survival or an overestimate of emigration.

 

In the Discussion section:

• Please clarify a little bit more the conclusions about colony-wide shifts, which are inferred indirectly.
• Separate and clearly state individual behaviour from those about population-level processes.
• Clarify what spatial scale is biologically meaningful in the interpretation of philopatry
• Present exact percentage differences and link them to spatial scale for survival.

Author Response

Please see the attachment

Author Response File: Author Response.pdf