Online Resource 3 – Baseline occurrence data and presence–absence matrices
Description

This resource contains baseline bird occurrence data at 2 × 2 km resolution for two survey periods: T1 (1999–2005) and T2 (2023–2024).
The datasets compile the results of 213 standardized transect surveys conducted within each sampling square, following national breeding bird atlas protocols.
These presence–absence data form the empirical basis for all analyses of species richness and occurrence changes presented in the study.

Contents
Table S1 — T1 presence–absence matrix (1999–2005)
Table S2 — T2 presence–absence matrix (2023–2024)

File: Table_S1_Table_S2.xlsx

Caption

Table S1–S2. Baseline presence–absence matrices for T1 and T2 at 2 × 2 km resolution.
Table S1 contains the dataset for the first survey period (T1, 1999–2005), derived from the Portuguese Breeding Bird Atlas.
Table S2 contains the corresponding dataset for the second survey period (T2, 2023–2024), based on 213 transect surveys conducted by the authors following national atlas protocols.

Data source

Equipa Atlas (2008) Atlas das aves nidificantes em Portugal (1999–2005).
ICNB, SPEA, PNM, SRAM, Assírio & Alvim, Lisboa. ISBN 978-972-37-1374-9

License

CC BY 4.0

Version

1.0 (2025-11-30)