Population trends of seabirds in Mexican Islands at the California Current System.

The Baja California Pacific Islands (BCPI) is a seabird hotspot in the southern California Current System supporting 129 seabird breeding populations of 23 species and over one million birds annually. These islands had a history of environmental degradation because of invasive alien species, human disturbance, and contaminants that caused the extirpation of 27 seabird populations. Most of the invasive mammals have been eradicated and colonies have been restored with social attraction techniques. We have recorded the number of breeding pairs annually for most of the colonies since 2008. To assess population trends, we analyzed these data and show results for 19 seabird species on ten island groups. The maximum number of breeding pairs for each nesting season was used to estimate the population growth rate (λ) for each species at every island colony. We performed a moving block bootstrap analysis to assess whether seabird breeding populations are increasing or decreasing. San Benito, Natividad, and San Jerónimo are the top three islands in terms of abundance of breeding pairs. The most widespread species is Cassin's Auklet (Ptychoramphus aleuticus) with 14 colonies. Thirty-one populations of 14 species are significantly increasing while eleven populations of seven species are decreasing. We did not find statistical significance for 19 populations, however, 15 have λ>1 which suggest they are growing. Twelve of the 18 species for which we estimated a regional population trend are significantly increasing, including seven surface-nesting species: Brandt's Cormorant (Phalacrocorax penicillatus), Brown Pelican (Pelecanus occidentalis), Caspian Tern (Hydroprogne caspia), Double-crested Cormorant (P. auritus), Elegant Tern (Thalasseus elegans), Laysan Albatross (Phoebastria immutabilis) and Western Gull (Larus occidentalis), and five burrow-nesting species: Ainley's (Hydrobates cheimomnestes), Ashy (H. homochroa) and Townsend's (H. socorroensis) Storm-Petrels, and Craveri's (Synthliboramphus craveri) and Guadalupe (S. hypoleucus) Murrelets. The BCPI support between 400,000 and 1.4 million breeding individuals annually. Our results suggest that these islands support healthy and growing populations of seabirds that have shown to be resilient to extreme environmental conditions such as the "Blob", and that such resilience has been strengthen from conservation and restoration actions such as the eradication of invasive mammals, social attraction techniques and island biosecurity.

Effect of malathion on the demography of Daphnia pulex Leydig and Diaphanosoma birgei Korinek (Cladocera).

Malathion is a common pesticide used to control insects in agricultural, domestic and industrial sectors in different parts of the world. In this work we evaluated the effects of sublethal concentrations of malathion on the survivorship and reproductive variables of two cladoceran species Daphnia pulex and Diaphanosoma birgei using standard life table demography method. Based on preliminary tests, we selected four sublethal concentrations of malathion for each cladoceran species. For D. pulex, the malathion concentrations were 0. 225, 0.45, 0.9 and 1.8ng I(-1) and for D. birgei, these were 0.0281, 0.0562, 0.1125, 0.225ng I(-1). Our results showed that in general, Daphnia pulex was less sensitive than Diaphanosoma birgei to malathion. The average lifespan of Daphnia pulex in controls was about 19 days while under similar conditions, that of D. birgei was about 21 days. For either cladoceran species, increased pesticide concentration resulted in decreased survival; this was more evident in the treatment containing the highest concentration of malathion (0.225 ng l(-1)) for D. birgei. Fecundity of D. pulex and D. birgei also decreased with increase in the concentration of malathion. For a given cladoceran species, compared to controls, the gross reproductive, net reproductive rates and the population growth rate significantly decreased due to malathion. Compared to the survivorship variables (age-specific survival, life expectancy and average lifespan), the reproductive parameters (gross reproductive rate, net reproductive rate and the rate of population increase) of the two cladoceran species were decreased by the pesticide.