Some Population Aspects of Common Tern Sterna hirundo Breeding in Algeria at a Small Mediterranean Island (East Coast of Algeria)

We present the first detailed study of population dynamics, breeding biology and egg measurement of Common Terns. During six years (from 2004 to 2009) of monitoring, from mid-May to mid-August, 74 Common Terns individual were recorded at Laouinet small island, El Tarf, northeast of Algeria, witha finite population growth rate that indicated an alarming population decline(λ = -0.62: Lambda). Sterna hirundo build its nests (n = 37) in the northeast at a mean distance of 7.58 m from the closest edge of rocks. The nests were closed and ovoid, constituted mainly of mussel shells Sandpit, stems and leaves. Incubation was performed by pairs of common tern and lasted 25.5 ±3.4 days. We recorded a clutch size of 1 to 3 eggs with mean clutch size of 2.45±0.65 (41.24±0.83 × 30.46±0.62 mm). The egg parameters (volume, mass, shape index) varied between the six years of the study. The egg volume (19.24±0.87) depended more on egg width (30.46±0.62), however the egg shape (0.73±0.20) depended negatively on the egg length (41.24±0.83) but not on the egg width. Our results also showed a stabilized hatching success and a best estimation of breeding success. The hatching success did not vary between years: 70.5% in 2004, 68.75% in 2005, 71.42% in 2006, 71.42% in 2007, 69.23% in 2008 and 69.23% in 2009.