Does parental heart rate affect embryonic heart rate during incubation? An experiment in Common Terns Sterna hirundo

Embryonic heart rate is a strong determinant of metabolic rate and the rate of embryonic development in oviparous species. In humans, embryonic heart rate is positively correlated with the heart rate of the mother. However, human embryos do not develop autonomously from the maternal circulatory system, making it impossible to separate maternal control from an independent embryonic adjustment of its heart rate to that of its mother. In birds, embryonic development does occur autonomously from the mother, while the embryo can auditively perceive the heart rate of the incubating parent. In this study, we used Common Terns (Sterna hirundo) to experimentally test whether the embryonic heart rate is affected by parental heart rate during incubation. We artificially incubated freshly laid eggs under standardized conditions and continuously exposed them to the sound of either a slow or fast parental heart rate throughout the first 18 days of embryonic development. At day 18 of embryonic development (a few days before hatching) there was no significant difference in the embryonic heart rate between both treatments. There was also no effect of treatment on either total duration of embryonic development or hatching success. We suggest that embryonic heart rate and development rate may not be affected by the heart rate of the parent because natural parental heart rates are very sensitive to external conditions that may fluctuate drastically, while embryos may need a relatively stable heart rate for optimal development.

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.

FIFTH REPORT OF THE COMMITTEE FOR ECUADORIAN RECORDS IN ORNITHOLOGY (CERO), WITH COMMENTS ON SOME PUBLISHED, UNDOCUMENTED RECORDS

Wepresent new distributional records of birds in Ecuador evaluated by the Committee for Ecuadorian Records in Ornithology (CERO) from November 2017 through June 2019. This report includes two species new to Ecuador (Pelecanoides garnotii, Conirostrum margaritae), five species with first documented country records (Thaumastura cora, Anous minutus, Setophaga pensylvanica, S. virens, Spiza americana), two species with first documented Galapagos records (Oceanodroma hornbyi, Egretta tricolor), remarkable range extensions for 15 species (Amazilia amazilia, Aramus guarauna, Vanellus chilensis, Attagis gayi, Anous stolidus, Sterna hirundo, Thalasseus elegans, T. sandvicensis, Eurypyga helias, Mycteria americana, Plegadis falcinellus, Gampsonyx swainsonii, Rosthramus sociabilis, Glaucidium peruanum, Thlypopsis sordida), new records of 16 rare species (Oressochen jubatus, Spatula cyanoptera, Podiceps major, Stercorarius longicaudus, Larus belcheri, Pelagodroma marina, Oceanodroma markhami, Egretta rufescens, Plegadis ridgwayi, Buteo swainsonii, Megascops koepckeae, Tyrannus albogularis, Setophaga castanea, Dolichonyx oryzivorus, Icterus chrysater, I. galbula) and additional records for 8 species. Finally, we invalidate previous records of Pyrilia pyrilia published in different sources, reject records of six species submitted to CERO, and discuss six previously published, undocumented records that might prove erroneous. CERO revises and updates the country bird list, which currently stands at 1696 species (1642 confirmed and documented; 54 undocumented).

Common Terns Sterna hirundo incubating a Red-necked Grebe Podiceps grisegena egg

During a study of Red-necked Grebes Podiceps grisegena in Lake Slagsmyren, Sweden, a pair of Common Terns Sterna hirundo were observed to have placed their two eggs on a deserted, floating nest of a Red-necked Grebe. Prior to this, the grebes had laid one egg of their own in the nest and this egg was included by the terns in their clutch and incubated by them. The species assignment of the odd egg was confirmed with DNA sequencing. A lack of natural nest sites for the terns to use at the lake could have caused this somewhat unusual choice of a nest site. I discuss possible explanations for adopting a foreign egg, including the adaptive behavioural response to roll an egg into the nest bowl to salvage lost eggs, the incubation stimulus that foreign eggs or egg-like objects potentially provide, and the limited egg discrimination abilities of Common Terns. The incubation of a foreign egg may reasonably be assumed to cost energy but to be of little benefit, if any, to the incubator.