Data Zone
Justification of Red List category
This species is listed as Endangered because it is estimated to have a very small population which is undergoing continuing declines owing to habitat loss and disturbance on its breeding grounds. It is also restricted to a very small area when breeding and these breeding grounds remain highly threatened.
Population justification
Estimates range from 100 pairs (G. Engblom in litt. 2005) to 5,000 pairs (M. Plenge in litt. 1999). Given that there are still unsurveyed sandy beaches away from the Pan-American Highway, the total is perhaps likely to fall in the range of 1,000-2,499 individuals. This equates to 667-1,666 mature individuals, rounded here to 600-1,700 individuals.
Trend justification
The population is suspected to be declining on the basis of continued destruction and degradation of breeding habitat, disappearance of breeding colonies in the last 30 years (e.g. Puerto Viejo and Mollendo in Peru) and population decline in some localities (Pampa Mejillones and La Portada in Chile).
Sternula lorata is restricted to the Humboldt Current Zone from north Peru to the peninsula of Mejillones in Chile (Enticott and Tipling 1997, Guerra-Correa 2007). Its movements are poorly known, but it has been recorded north to central Ecuador (Enticott and Tipling 1997). There are now only four confirmed breeding sites in Peru, at Pampa Lechuzas, Yanyarina, Paraiso and Pacasmayo (Zavalaga et al. 2008a), and nine in Chile, all of which are located in Mejillones and nearby areas (Guerra-Correa 2007). In Chile all colonies have been found in the desert plains, generally within 1 km of the coast, but in other locations colonies have also been found on sandy beaches associated with wetlands. A well-known former breeding site at Puerto Viejo is now heavily developed and no longer supports breeding birds (Zavalaga et al. 2008a), and population declines have been noted at Pampa Mejillones and La Portada in Chile. One locality was previously reported to have tens of thousands of individuals, but the population is now thought to be significantly reduced, as the numbers at all sites are estimated at 950-1,100 individuals and 150 to 160 pairs (Guerra-Correa 2007). Some reports suggest that the population may have declined by 50% in the last 10 years (Luchsinger 2007). However, there are still unsurveyed sandy beaches away from the Pan-American Highway that could be suitable for nesting, and old colonies that have not been visited since their discovery decades ago, while signs of previously unknown breeding sites have recently been recorded in La Libertad, Peru (Amorós 2011); the total is therefore likely to fall in the range of 1,000-2,500 individuals.
It breeds either on broad sandy beaches and dunes (100-200 m from the high tide mark) associated with wetlands (Zavalaga et al. 2008a), or in desert plains 1-3 km inland (Vilina 1998, Guerra et al. 2003, Zavalaga et al. 2008a). The shallow waters of wetlands are thought to offer optimal conditions for foraging, both within and outside the breeding season (Zavalaga et al. 2009). Egg-laying is asynchronous both within and between groups, and occurs from August to February (Vilina 1998, Guerra et al. 2003), particularly October to late January (Zavalaga et al. 2008b). Clutch size is one or two eggs, but usually only one chick fledges (Vilina 1998, Guerra et al. 2003). To counteract high levels of predation it nests in homogeneous habitat in small groups (3-25 nests), loosely aggregated, with inter-nest distances usually over 100 m (Vilina 1998, Zavalaga et al. 2008b), thus making nests difficult to detect (Zavalaga et al. 2008a). Eggs and chicks are well camouflaged with the bare ground. Inland nesting is believed to be a strategy to reduce risk from terrestrial predation, as predators often patrol closer to the shore. Birds are known to be absent during El Niño events (Zavalaga et al. 2008a) and do not attempt to breed (Zavalaga et al. 2008b). Post-breeding dispersal occurs from April until July, to unknown areas, probably offshore (Mackiernan et al. 2001). During the 1997-1998 El Niño event, hundreds were sighted 25-200 km offshore, suggesting they can disperse widely during oceanographic anomalies (Zavalaga et al. 2008a). It generally forages in inshore areas, but is occasionally seen 10-70 km offshore (Mackiernan et al. 2001). Main prey items include Anchovies Engraulis ringens, South Pacific Sauris Scomberesox saurus scombroides (Guerra et al. 2003), Peruvian Silversides Odonthestes regia regia and Mote Sculpins Normanychtis crockeri. Prey items found in nests measured less than 8 cm, indicating a prey size limit imposed by chick body size (Zavalaga et al. 2008b).
As a ground nesting species, the Peruvian Tern is vulnerable to human activities, which can cause disturbance of nesting adults and a subsequent loss of reproductive success, as well as the loss and degradation of vital nesting habitat. Local small scale harvesting of marine resources such as seaweed, fish and shellfish has been recorded at multiple breeding and non-breeding sited (e.g. Pacasmayo and Paraiso) and is associated with the use of 4x4 vehicles on the beach, introduction of dogs and construction of small fishing camps (Zavalaga et al. 2008ab, Zavalaga et al. 2009). Similar disturbance also occurs due to recreational activities such as off-road driving and dog walking, with disturbance intensifying in Paraiso between 2003 and 2008 (Zavalaga et al. 2009). Feral Cats Felis catus were recorded at multiple breeding sites in 2008, including Isla Lobos de Tierra and Tres Hermanas-Yanyarina and have been seen to attack Peruvian Terns (Zavalaga et al. 2008a) and may deter settlement and breeding (Zavalaga et al. 2009). Foxes Pseudolopex spp. have been recorded at almost all nesting sites studies and are considered among the main predators of tern nests (Zavalaga et al. 2008ab, 2009).
Well known breeding sites have been lost to heavy residential development (Zavalaga et al. 2008a), including the building of shanty towns and summer homes in Puerto Viejo as well as residential and commercial development at Pampa de Mejillones, Northern Chile, causing a reduction in the breeding habitat available to the largest colony of Peruvian Terns (Braby 2011). The expansion of tourist and recreational areas is also a threat to breeding sites (Zavalaga et al. 2009). Conversion of desert plains into agricultural land at nesting sites (e.g. Punta Literas-Pativilica) through the use of irrigation (Zavalaga et al. 2009) represents a further loss of breeding habitat. Significant as only a handful of breeding sites known. Abstraction for irrigation degrades wetland foraging habitat, with the construction of 1.5m sand dam at the Ite site in 2008 increasing water levels in the area, possibly making it unsuitable for the terns, with birds recorded in 2007 but not in 2008 (Zavalaga 2009). Oil exploration near tern nests at San Pedro de Vice is likely to have destroyed possible nesting sites, as well as causing irreversible damage to mangrove ecosystem which Peruvian Terns use to forage (Zavalaga et al. 2009).
Further to this, breeding success at nesting sites in 1980s El Niño Southern Oscillation (ENSO) event was reported to drop to 0% at some sites, with breeding not attempted or chicks dying of starvation. This species has been highlighted as being vulnerable to the impacts of ENSO due to the effects of decreased prey availability.
Conservation Actions Underway
In Chile, CONAMA (2006) has recognized the species as threatened with extinction, and it has been officially classified as Endangered. In Peru it has been recognized as Vulnerable (Zavalaga et al. 2008a).
Text account compilers
Harding, M., Palmer-Newton, A., Khwaja, N., Sharpe, C.J., Lascelles, B., Martin, R., Calvert, R., Benstead, P., Anderson, O., Capper, D., Moreno, R., Stuart, A., Symes, A., Frere, E.
Contributors
Engblom, G., Guerra, C., Jaramillo, A.P., Plenge, M.A., Tello, A. & Zavalaga, C.
Recommended citation
BirdLife International (2024) Species factsheet: Peruvian Tern Sternula lorata. Downloaded from
https://datazone.birdlife.org/species/factsheet/peruvian-tern-sternula-lorata on 23/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/12/2024.