Background The Maghreb Magpie (Pica mauritanica) is an endemic North African species. Available knowledge on this species is limited to historic descriptive data with no ecological information provided. Populations continue to dramatically decline in Tunisia, where only one relic population survives. Investigating the breeding biology of this species is essential for conservation purposes. The purpose of this study was to increase our understanding of the Tunisian relic population and provide detailed data on breeding biology over two breeding seasons (2017 and 2018).

Methods This study occurred on a private farm of 650 ha, located 10 km from Dhorbania village at Kairouan Governorate, in central Tunisia. Active nests were monitored weekly during egg laying period and twice a week during hatching period. The Ivlev's electivity index was used to assess whether the frequency of use of nesting trees and bushes matched their availability in the study area. We recorded nest measurements and positions, and compared them using Wilcoxon signed-rank test. Variations of breeding parameters as number of eggs laid, hatchlings, and fledglings over years were performed using Mann–Whitney U-test and χ² tests. We used a Generalized Linear Mixed Model (GLMM) to investigate how egg volume varied with clutch size and laying date.

Results We investigated clutch size, egg size, hatching and fledging success, and evaluated how these parameters varied according to laying date and nest characteristics. Clutch size averaged 5.00 ± 0.19 but was significantly greater in 2017. Hatching success was 2.78 ± 0.34 eggs hatched per nest and fledging success reached 1.69 ± 0.30 young/nest. Causes of nest failure included the depredation of nestlings by shrikes, cobras and rats (e.g. Lanius meridionalis, Naja haje and Rattus rattus), death of parents by the Black-shouldered Kite (Elanus caeruleus) and nest parasitism by the Great Spotted Cuckoo (Clamator glandarius). Clutch size, brood size and fledgling success were unaffected by laying date, nest volume and nest elevation. Egg volume decreased with laying date but was unaffected by clutch.

Conclusion Our study provides the first and only detailed data on reproductive parameters of the Maghreb Magpie in its entire geographic range (North Africa). Information gleaned from this study provides valuable information for monitoring and long-term conservation plans of the endangered Tunisian Magpie population. Additionally, our data provide an avenue of large-scale comparative studies of the reproductive ecology of the magpie complex.