Seasonal variation in coastal marine habitat use by the European shag: Insights from fine scale habitat selection modeling and diet

Michelot, Candice; Pinaud, David; Fortin, Matthieu; Maes, P.; Callard, Benjamin; Leicher, Marine; Barbraud, Christophe

doi:10.1016/j.dsr2.2017.04.001

Cited by 13 publications

(7 citation statements)

References 57 publications

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“…Theory suggests that diet diversifies when predominant prey become scarce and/or lessen in profitability (Stephens & Krebs 1986), and empirical evidence in other seabird studies supports this (Croxall et al 1999, Cosolo et al 2011. Shags exploit a wide range of prey (Barrett 1991, Velando & Freire 1999, Lilliendahl & Solmundsson 2006, Cosolo et al 2011, Michelot et al 2017) and can adjust their foraging behaviour in response to a change in availability of different prey types within their foraging range (Wanless et al 1998, Daunt et al 2007, Bogdanova et al 2014, Michelot et al 2017. Changes in the availability of sandeels, non-sandeels or both may have contributed to the diet shift in our study population since many fish species have experienced changes in abundance and distribution in the N orth Sea linked to ocean warming (Perry et al 2005, Hiddink & ter Hofstede 2008, Heath et al 2012.…”

Section: Diet Trendsmentioning

confidence: 90%

From days to decades: short- and long-term variation in environmental conditions affect offspring diet composition of a marine top predator

Howells¹,

Burthe²,

Green³

et al. 2017

Mar. Ecol. Prog. Ser.

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Long-term changes in climate are affecting the abundance, distribution and phenology of species across all trophic levels. Short-term climate variability is also having a profound impact on species and trophic interactions. Crucially, species will experience long-and short-term variation simultaneously, and both are predicted to change, yet studies tend to focus on only one of these temporal scales. Apex predators are sensitive to long-term climate-driven changes in prey populations and short-term effects of weather on prey availability, both of which could result in changes of diet. We investigated temporal trends and effects of long-and short-term environmental variability on chick diet composition in a North Sea population of European shags Phalacrocorax aristotelis between 1985 and 2014. The proportion of their principal prey, lesser sandeel Ammodytes marinus, declined from 0.99 (1985) to 0.51 (2014), and estimated sandeel size declined from 104.5 to 92.0 mm. Concurrently, diet diversification increased from 1.32 (1985) to 11.05 (2014) prey types yr −1 , including members of the families Pholidae, Callionymidae and Gadidae. The relative proportion of adult to juvenile sandeel was greater following low sea surface temperatures (SSTs) in the previous year. In contrast, the proportion of Pholidae and prey richness were higher following high SST in the previous year. Within a season, the proportion of sandeel in the diet was lower on days with higher wind speeds. Crucially, our results showed that diet diversification was linked to trends in SST. Thus, predicted changes in climate means and variability may have important implications for diet composition of European shags in the future, with potential consequences for population dynamics.

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Section: Diet Trendsmentioning

confidence: 90%

From days to decades: short- and long-term variation in environmental conditions affect offspring diet composition of a marine top predator

Howells¹,

Burthe²,

Green³

et al. 2017

Mar. Ecol. Prog. Ser.

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“…Diet composition was estimated following Michelot et al (2017). First, we calculated the proportion of each prey group by biomass in each pellet (biomass of a prey group in a pellet / total biomass in the same pellet).…”

Section: Diet Datamentioning

confidence: 99%

Reproductive success in the European shag is linked to annual variation in diet and foraging trip metrics

Lorentsen¹,

Mattisson²,

Christensen‐Dalsgaard³

2019

Mar. Ecol. Prog. Ser.

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Seabird populations have declined worldwide, and several of the potential threats are of anthropogenic origin. To understand how changes in seabird populations relate to environmental conditions it is important to know the functional relationships between prey availability and foraging behaviour, prey choice and breeding performance over several years. This was studied by linking breeding success of European shag Phalacrocorax aristotelis to variation in diet composition, and investigating the underlaying mechanism driving this variation, primarily based on behavioural costs associated with foraging, such as foraging range and diving effort. We obtained demographic data and foraging trip metrics (using GPS-loggers and time−depth recorders) from a shag colony at Sklinna, Central Norway, during the 2011−2016 breeding seasons. Breeding population size was closely and positively correlated with breeding success, which in turn was positively correlated with the proportion of saithe Pollachius virens in the diet. When the dietary proportion of uncommon prey species increased, breeding success decreased. Breeding success was negatively influenced by increasing distance travelled and accumulated dive depths on an annual basis. Summed dive depths were greatest when prey species other than saithe dominated the diet. We found that in years with low availability of saithe fewer shags bred, and those that did had lower breeding success. This indicates that in years with poor feeding conditions, there might not be sufficient resources in the foraging area to support the whole breeding population of shags.

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“…Crucially, effects on fitness are likely to depend on the relative profitability of different prey types throughout the annual cycle (Hislop et al 1991;Litzow et al 2004). Due to the difference in habitat associations between prey types, the dietary change observed may also have important implications for shag foraging distributions (Bogdanova et al 2014;Michelot et al 2017). The increase in proportion of non-sandeels in the diet could alter interactions with anthropogenic activities, such as offshore renewable developments or recreation.…”

Section: Demographic and Conservation Implicationsmentioning

confidence: 99%

“…However, sandeel availability varies among seasons since they are present in the water column during the spring and summer, but are buried in the sand during the winter, apart from a brief period when they emerge to spawn (Wright and Bailey 1993). Furthermore, environmental conditions, habitat use and energetic costs also vary between seasons (Daunt et al 2014;Michelot et al 2017). Thus, any changes in overall prey abundance or availability during the study might have different effects on diet composition at different times of the year.…”

Section: Introductionmentioning

confidence: 99%

Pronounced long-term trends in year-round diet composition of the European shag Phalacrocorax aristotelis

et al. 2018

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Populations of marine top predators are exhibiting pronounced demographic changes due to alterations in prey availability and quality. Changes in diet composition is a key potential mechanism whereby alterations in prey availability can affect predator demography. Studies of long-term trends in diet have focused on the breeding season. However, long-term changes in non-breeding season diet is an important knowledge gap, since this is generally the most critical period of the year for the demography of marine top predators. In this study, we analysed 495,239 otoliths from 5888 regurgitated pellets collected throughout the annual cycle over three decades (1985-2014) from European shags Phalacrocorax aristotelis on the Isle of May, Scotland (56°11′N, 02°33′W). We identified dramatic reductions in the frequency of lesser sandeel Ammodytes marinus occurrence over the study, which was more pronounced during the non-breeding period (96% in 1988 to 45% in 2014), than the breeding period (91-67%). The relative numerical abundance of sandeel per pellet also reduced markedly (100-13% of all otoliths), with similar trends apparent during breeding and non-breeding periods. In contrast, the frequencies of Gadidae, Cottidae, Pleuronectidae and Gobiidae all increased, resulting in a doubling in annual prey richness from 6 prey types per year in 1988 to 12 in 2014. Our study demonstrates that the declining importance of the previously most prominent prey and marked increase in diet diversity is apparent throughout the annual cycle, suggesting that substantial temporal changes in prey populations have occurred, which may have important implications for seabird population dynamics.

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Seasonal variation in coastal marine habitat use by the European shag: Insights from fine scale habitat selection modeling and diet

Cited by 13 publications

References 57 publications

From days to decades: short- and long-term variation in environmental conditions affect offspring diet composition of a marine top predator

From days to decades: short- and long-term variation in environmental conditions affect offspring diet composition of a marine top predator

Reproductive success in the European shag is linked to annual variation in diet and foraging trip metrics

Pronounced long-term trends in year-round diet composition of the European shag Phalacrocorax aristotelis

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