Breeding Seasons

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2016 breeding season summary 

The 2016 breeding season on the Isle of May NNR proved to be mixed following the general success of 2014 and 2015.  Breeding in 2016 commenced early for European shags but late for black-legged kittiwakes and Atlantic puffins.  

Of the six study species, European shags had their most successful season on record, while black-legged kittiwakes and northern fulmars were above average.  Atlantic puffins had an average season while common guillemots had a below average breeding season. Razorbills had the worst season on record.   Return rates were above the long term average in all study species except Atlantic puffins, which were very low.  Sandeels (Ammodytes sp.) remained the main food of young razorbill, Atlantic puffins, shags and kittiwakes.  The diet of common guillemots was dominated by clupeids.  The main results are as follows:

Northern fulmar breeding success (0.43 chicks per incubating pair) was above average.

European shags had the most successful season on record (2.1 chicks per pair).  Return rate was above average at 88.9%.  Diet was dominated by sandeel which occurred in 73.5% of samples. 

Black-legged kittiwakes had a good season with productivity (0.78 chicks per completed nest) being well above average.  Adult return rate (88%) was also well above the long term average. The proportion of sandeel in the diet (53% by biomass) was below average whereas the proportion of clupeid (43% by biomass) was high.  

Guillemots had a relatively poor breeding season (0.66 chicks leaving per pair laying).  Return rate of adults (93.6%) was normal.  Adults fed their chicks mainly small sprats (83% by number).

Razorbill breeding success (0.45 chicks leaving per pair) was the lowest on record but adult return rate (87.5%) was above average. Chick diet contained more sandeel (58% of loads) than clupeids (42%).

Atlantic puffins had an average season with 0.76 chicks fledging per pair laying.  The return rate for adults (72.3%) was well below average. Chicks were fed mainly sandeels (88.7% by number) with Clupeidae (mainly sprats) and rockling contributing 3.5% and 1.9% respectively.

 

2015 breeding season summary 

The 2015 breeding season on the Isle of May NNR proved to be another good year following the general success of 2014.  Breeding in 2015 commenced early for most species, especially European shags and Black-legged kittiwakes.   

Of the six study species, northern fulmar, European shags and black -legged kittiwakes had one of their most successful seasons on record.  Common guillemot and Atlantic puffin had above average breeding seasons while razorbill returned to typical levels after four poor years.   Return rates were above the long term average in all five study species.  Sandeels (Ammodytes sp.) remained the main food of young razorbill, Atlantic puffins, shags and kittiwakes.  The diet of common guillemots was dominated by clupeids.  

Highlights

  • Northern fulmar breeding success (0.52 chicks per incubating pair) was well above average.
  • European shags had an above average breeding season (1.91 chicks per pair).  Return rate was above average at 87.9%.  Diet was dominated by sandeel which occurred in 94% of samples.  
  • Black-legged kittiwakes had an excellent season with productivity (1.07 chicks per completed nest) being well above average.  Adult return rate (84%) was also well above the long term average. The proportion of sandeel in the diet (66% by biomass) was below average whereas the proportion of clupeid (22% by biomass) was typical.   
  • Guillemots had an average breeding season (0.78 chicks leaving per pair).  Return rate of adults (93.1%) was above average.  Adults fed their chicks mainly on medium-sized sprats (91% by number). 
  • Razorbill breeding success (0.60 chicks leaving per pair) was typical and adult return rate (86.2%) was typical. Chick diet contained more sandeel (59% of loads) than clupeids (40%).
  • Atlantic puffins had an average season with 0.75 chicks fledging per pair laying.  The return rate for adults (89.8%) was above average. Chicks were fed mainly sandeels (87% by number) with Clupeidae (mainly sprats) and Gadiformes (mainly rockling) contributing 7% and 6% respectively. 

 

2014 breeding season summary

Following on from three mixed years, 2014 proved to be a good breeding season on the Isle of May NNR.  After a late season in 2013 due largely to poor weather through much of the winter and early spring in the region, breeding in 2014 commenced on typical dates for most species.   

Of the six study species, Northern fulmars had the most successful season on record, while European shags had an above average season and Black-legged kittiwakes the most successful season since 1987. In contrast, razorbills had a poor breeding season. Return rates were similar to the long-term average in all five study species. Sandeels (Ammodytes sp.) remained the main food of young Atlantic puffins, shags and kittiwakes. The diet of razorbills and common guillemots was dominated by clupeids.

Highlights

  • Northern fulmar breeding success (0.56 chicks per incubating pair) was the highest on record.
  • European shags had an above average breeding season (1.58 chicks per pair).  Return rate was normal at 77.7%.  Diet was dominated by sandeel which occurred in 86% of samples.
  • Black-legged kittiwakes had an excellent season with productivity (1.17 chicks per completed nest) being the highest since 1987.  Adult return rate (78%) was close to the long term average. The proportion of sandeel in the diet (77% by biomass) was also typical as was the proportion of clupeid (19% by biomass).
  • Guillemots had an average breeding season (0.72 chicks leaving per pair). Return rate of adults (88.7%) was also normal.  Adults fed their chicks almost entirely on medium-sized sprats (94% by number).
  • Razorbill breeding success (0.53 chicks leaving per pair) was poor but adult return rate (91.9%) was typical. Chick diet contained more clupeids (65% of loads) than sandeels (32%).
  • Atlantic puffins had an average season with 0.68 chicks fledging per pair laying. The return rate for adults (83.4%) was normal. Chicks were fed mainly sandeels (84% by number) with Clupeidae (mainly sprats) and Gadiformes (mainly rockling) both contributing 8%.

2013 breeding season summary

Following on from two mixed years, 2013 proved to be another variable breeding season on the Isle of May NNR. Poor weather through much of the winter and early spring delayed the breeding season for most species and reduced the breeding numbers of some species, most notably European shags.

Of the six study species, Northern fulmars had the most successful season since 2002 while European shags had an above average season. In contrast, razorbills had the lowest productivity on record, while black-legged kittiwakes were also well below average. Atlantic puffins and common guillemots had slightly below average seasons.

Return rates were above average for Atlantic puffin, common guillemot and black-legged kittiwake, below average for razorbill and the third lowest on record for European shags.

Lesser sandeels (Ammodytes marinus) remained the main food of young Atlantic puffins while European shags fed mainly on butterfish. Although the diet of razorbills and kittiwakes was dominated by sandeels the proportion was below average. Common guillemots fed their young mainly on clupeids.

Highlights

  • Northern fulmar breeding success (0.47 chicks per incubating pair) was the highest since 2002.
  • European shags had an above average breeding season (1.20 chicks per pair) despite the late start and much reduced numbers. Return rate was one of the lowest on record at 43%. Diet was dominated by butterfish (40% by biomass) with sandeels making up only 28% by mass of the diet, the equal lowest on record.
  • Black-legged kittiwakes had a poor season with productivity (0.41 chicks per completed nest) being below the long-term average. Adult return rate (81%) was above average. The proportion of sandeel in the diet (65% by biomass) was below average while the proportion of clupeid (29% by biomass) was above average.
  • Guillemots had a slightly below average breeding season (0.69 chicks leaving per pair). Return rate of adults (91.3%) was similar to the previous three years and above the long term average. Adults fed their chicks mainly on medium-sized sprats (86% by number).
  • Razorbill breeding success (0.48 chicks leaving per pair) was the lowest on record. Adult return rate (76.9%) was considerably below average. Chick diet contained slightly more sandeels (56% of loads) than small-sized sprats (44%).
  • Atlantic puffins had a slightly below average season with 0.70 chicks fledging per pair laying. The return rate for adults (85.4%) was above average despite the wreck just prior to the breeding season. Chicks were fed mainly sandeels (76% by number) with Gadidae, mainly consisting of rockling, also numerous (14% by number).

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2012 breeding season summary

Following a mixed year in 2011 and two successful breeding seasons in 2009 and 2010, another variable year was noted in 2012 for seabirds on the Isle of May NNR.  A strong westerly storm in mid-May affected the breeding of many individuals and, although there were some relay attempts, it may have depressed breeding success for some species. Exceptionally high rainfall also affected the breeding of some species, most notably Atlantic puffins.

Of the six study species, Black-legged kittiwakes had the most successful season since 1989 while Common guillemots and European shags had an above average season. In contrast, Northern fulmars had the lowest productivity on record. Atlantic puffins and razorbills had below average seasons with only three and two worse years respectively. Return rates were above average for all species with Atlantic puffin the second highest since 2001.  

Lesser sandeels remained the main food of young Atlantic puffins and European shags, whilst they comprised a greater proportion of the diet of razorbills and kittiwakes than recorded in recent years. Common guillemots fed their young mainly on clupeids.

Although lesser sandeels remained the main food of young Atlantic puffins and European shags, common guillemots fed their young mainly on clupeids. Razorbill chick diet was evenly split between sandeels and clupeids. Kittiwake diet was dominated by clupeids; however, these clupeids were small in size so sandeels were the most important prey in terms of total biomass.

Highlights

  • Northern fulmar breeding success (0.13 chicks per incubating pair) was the lowest on record.
  • European shags had a less successful breeding season (1.18 chicks per pair) than the previous four years, but breeding success was still above the long term average. Return rate was markedly above the long term mean at 93%.  The food was varied with sandeels making up 68% by mass of the diet.
  • Black-legged kittiwakes had a good season with productivity (0.98 chicks per completed nest) being the highest since 1989 and considerably above the long-term average. Adult return rate (80%) was also above average. The proportion of sandeel in the diet (87% by biomass) was above average while the proportion of clupeid (12% by biomass) was below average.   
  • Guillemots had an above average breeding season (0.79 chicks leaving per pair). Return rate of adults (91.8%) was similar to the previous two years and above the long term average. Adults fed their chicks mainly on medium-sized sprats (85% by number).
  • Razorbill breeding success (0.56 chicks leaving per pair) was an improvement on 2011 but still well below average. Adult return rate (92.9%) was considerably above average. Chick diet was dominated by sandeels (91.5% of loads) with small-sized sprats the only other significant prey item (8.5%).
  • Atlantic puffins had a poor season with 0.57 chicks fledging per pair laying. This was markedly below average and largely due to high rainfall flooding burrows. The return rate for adults (89.7%) was high and continued the improvement noted in the previous three years. Chicks were fed mainly sandeels (90.3% by number) with Gadidae, mainly consisting of rockling, also numerous (7.8% by number).

2011 breeding season summary

Following two successful breeding seasons in 2009 and 2010, 2011 was a mixed year for seabirds on the Isle of May NNR.  A severe westerly storm in late May affected the breeding of many individuals and, although there were some relay attempts, it may have depressed breeding success for some species.

Of the six species studied intensively, Atlantic puffins had the most productive breeding season since 1995, while black-legged kittiwakes had the second most successful season since 1989.  European shag had an above average breeding season, while common guillemots had an average season, with northern fulmar slightly below average.  In contrast razorbills had the lowest productivity on record.  Return rates were above average for all species with razorbills having the joint second highest on record and common guillemot the second highest since 1997.

Although lesser sandeels remained the main food of young Atlantic puffins and European shags, common guillemots fed their young mainly on clupeids. Razorbill chick diet was evenly split between sandeels and clupeids. Kittiwake diet was dominated by clupeids; however, these clupeids were small in size so sandeels were the most important prey in terms of total biomass.

Highlights

  • Northern fulmar breeding success (0.36 chicks per incubating pair) was a slight increase on 2010 but still below the long term average.
  • European shags had a successful breeding season (1.52 chicks per pair), which was above the long term average but lower than the previous three years. Return rate was well above the long term mean at 93%.  The food was very consistent with sandeels making up 92% by mass of the diet.
  • Black-legged kittiwakes had a good season with productivity (0.87 chicks per completed nest), the highest since 2000 and well above the long-term average.  Adult return rate (80%) was also above average. The proportion of sandeel in the diet (51% by biomass) was below average while the proportion of clupeid (35% by biomass) was the second highest on record.
  • Guillemots had an average breeding season (0.71 chicks leaving per pair).  Return rate of adults (92.1%) was similar to the previous two years and above the long term average. Adults fed their chicks mainly on medium-sized sprats (92% by number).
  • Razorbill breeding success (0.52 chicks leaving per pair) was the lowest on record. Adult return rate (95.2%) equalled the second highest ever recorded on the Isle of May. Chick diet was fairly evenly split between sandeels (52%) and medium-sized sprats (46%).
  • Atlantic puffins had a successful season with 0.79 chicks fledging per pair laying. The return rate for adults (87.9%) was high and continued the improvement noted in the previous two years. Chicks were fed mainly sandeels (69% by number) with rockling also numerous (21% by number).

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2010 breeding season summary

After a series of very poor breeding seasons for seabirds on the Isle of May NNR, the 2010 season continued the marked improvement shown in 2009 for most species. Overall the season was one of the most successful in recent years.

Of the six species studied intensively, European shag had its highest productivity on record with only black-legged kittiwake and fulmar having productivity below average. All other species studied had their most productive season for at least seven years. European shags had the highest return rate on record, while return rates for all other species were the highest since at least 2003.

Although lesser sandeels remained the main food of young Atlantic puffins, razorbills and common guillemots fed their young mainly on clupeids, while European shags brought in mainly sandeels aged one year or older. For the first year since this study began clupeids formed a larger biomass than sandeels in the diet of black-legged kittiwakes.

Highlights

  • Northern fulmar breeding success (0.34 chicks per incubating pair) was lower than 2009 and below the long term average.
  • European shags had the most successful season on record (2.04 chicks per pair), eclipsing the previous record set last year. Return rate was the highest on record at 95%. Unlike the previous four years, the food was very consistent, with sandeels making up 91.5% by mass of the diet. Examination of sandeel otoliths indicated that all were from the adult age classes.
  • Black-legged kittiwakes had a poor season with productivity (0.29 chicks per incubated nest) well below the long-term average. However, some plots suffered unusually high predation by a pair of carrion crows during incubation and from gulls during chick-rearing. Adult return rate (89%) was the highest since 1988. The proportion of sandeel in the diet (44% by biomass) was the lowest on record, while the proportion of clupeid (55% by biomass) was the highest.
  • Guillemots had a successful breeding season (0.80 chicks leaving per pair), which continued the improvement recorded in 2009 after a series of poor breeding seasons. Similarly, return rate of adults (92.4%) was similar to 2009 and close to the long-term average, following low levels the two previous winters. Adults fed their chicks mainly on medium-sized sprats (84% by number).
  • Razorbill breeding success (0.68 chicks leaving per pair) was above the long-term average. Adult return rate (95.2%) was the second highest ever recorded on the Isle of May. Chick diet was mainly medium-sized sprats that were present in 67% of the loads.
  • Atlantic puffins had a successful season with 0.74 chicks fledging per pair laying. The return rate for adults (90.9%) was high and continued the improvement noted in 2009 following the poor showing over the two previous winters. Chicks were mainly fed 0 group sandeels (68% by number, 54% by biomass). Although sprats made up only 3% by number, their large size resulted in their contributing 40% of the diet by weight.

2009 breeding season summary

After a series of very poor breeding seasons for seabirds on the Isle of May NNR, it was especially pleasing to see species doing markedly better in 2009, and overall the season was the most successful in recent years.

Of the six species studied intensively, European shag had its highest productivity on record with only razorbill having productivity below average. All other species studied had their most productive season for at least four years. Return rates were much higher than the previous two seasons for all species with only black-legged kittiwake below the long-term average. Although lesser sandeels remained the main food of young Atlantic puffins, razorbills and black-legged kittiwakes, common guillemots fed their young mainly on clupeids, while European shags brought in a wide variety of bottom-living fish.

Comparatively few 1+ group sandeels were present in food samples during the chick-rearing period, however 0 group appeared in large numbers and were substantially longer than in recent years. No snake pipefish were noted in the seabird diet having been conspicuous in the previous four years.

Highlights

  • Northern fulmar breeding success (0.44 chicks per incubating pair) was a large increase on the previous two years and slightly above average.
  • European shags had the most successful season on record (2.02 chicks per pair), eclipsing the previous record set last year. Return rate was high at 89.6%, well above average and the highest for six years. As in the previous three years, the food was unusually varied with sandeels making up 51.6% by mass of the diet. Examination of sandeel otoliths indicated that 91% were from the 0 group age class.
  • Black-legged kittiwakes had a good season with productivity (0.70 chicks per incubated nest) the highest since 2005 and well above the long-term average. Adult return rate (71.3%) was an improvement after two very poor years but was still below the long-term average. The proportion of sandeel in the diet (89% by biomass) was the highest since 2005.
  • Guillemots had a successful breeding season (0.75 chicks leaving per pair) compared to recent years. Return rate of adults (92.0%) was normal following the low levels of the two previous winters. Adults fed their chicks mainly on sprats (67% by number) with sandeels (28%) the main alternative.
  • Razorbill breeding success (0.61 chicks leaving per pair) was below the long-term average. Adult return rate (97.3%) was the highest ever recorded on the Isle of May. Chick diet was almost entirely 0 group sandeels.
  • Atlantic puffins had a successful season with 0.72 chicks fledging per pair laying. The return rate for adults (84.7%) was normal following the poor showing over the two previous winters. Chicks were mainly fed 0 group sandeels (91% by number, 92% by biomass) that were substantially longer than during the last decade.

2008 breeding season summary

The 2008 season on the Isle of May was mixed. Of the six species studied intensively, European shag had its highest productivity on record whereas northern fulmar had its worst ever season. Atlantic puffin showed a marginal improvement on the lowest productivity experienced in 2007. Common guillemot productivity was well up on the previous year but, as with razorbill, was still below average, while black-legged kittiwakes had the worst season for ten years. Weather conditions were not exceptional so difficult feeding conditions were thought likely to be the main reason for such low productivity in most species.

Return rates, although well below average, were slightly up for black-legged kittiwake, Atlantic puffin and European shag, while for common guillemot it was the lowest on record. Although lesser sandeels remained the main food of young Atlantic puffins, razorbills and black-legged kittiwakes, common guillemots fed their young mainly on clupeids, while European shags brought in a wide variety of bottom-living fish. Comparatively few 1+ group sandeels were present in food samples during the chick-rearing period. Far fewer snake pipefish were noted in the seabird diet than in the previous three years.

Highlights

  • Northern fulmar breeding success (0.20 chicks per incubating pair) was the worst on record. Furthermore, this figure is an overestimate since a white-tailed eagle was observed predating on fulmar chicks late in the season, including one confirmed to be from a monitoring plot. The full impact of this eagle on fulmar breeding success is not known.
  • European shags began breeding earlier than in 2007 and had the most successful season on record. Shag was the only study species for which productivity (1.9 chicks per pair) was above the long-term mean. Following high mortality during the winter of 2006/07, return rate increased to 70.6% but was still below the long-term mean. As in the previous two years, the food was unusually varied with sandeels making up 48% by mass of the diet. Of sandeel otoliths, 40% were from older (1 group or older) fish whereas in 2007 all had been from this age class.
  • Black-legged kittiwakes had a very poor season with productivity (0.23 chicks per incubated nest) the lowest since 1999 and well below the long term average. Adult return rate (66.4%) was poor with only two other years showing lower values. The proportion of sandeel in the diet (59% by biomass) was the third lowest recorded, with high proportions of clupeid (20%) and rockling (12%) recorded.
  • Although better than in 2007, breeding success of common guillemots (0.63 chicks per pair laying) continued a worrying long-term decline. As in the previous three years, many chicks were left unattended but, surprisingly, few were taken by gulls. Return rate of adults (75.0%) was the lowest on record. Adults fed their chicks mainly on sprats (76%) with sandeels (20%) the main alternative.
  • Razorbill breeding success (0.58 chicks leaving per pair) was well below the long-term average, due mainly to unusually poor chick survival. Adult return rate (69.4%) was well down on the long-term average. Chicks were fed mainly 0-group sandeels.
  • The breeding success of Atlantic puffins at 0.48 fledged per pair laying was the second lowest on record. Return rate for adults (59.4%) was also the second lowest on record. This was the second year in a row of poor adult return rate, following the lowest ever in 2007. Chicks were mainly fed 0-group sandeels (63% by number, 73% by biomass).

2007 breeding season summary

The 2007 season was an exceptionally poor one for most species on the Isle of May. Of the six species studied intensively, European shag and razorbill had an average season but common guillemot, Atlantic puffin and Northern fulmar all had the worst season on record, while black-legged kittiwakes had the worst season for nine years.

Severe weather conditions played a part in the poor breeding season but difficult feeding conditions were still likely to be the main reason for such low productivity. Return rates were also at all-time lows for Common guillemot, Atlantic puffin and Black-legged kittiwake and well below average for shag. Although lesser sandeels remained the main food of young Atlantic puffins, razorbills and black-legged kittiwakes, common guillemots fed their young mainly on clupeids, while European shags brought in a wide variety of bottom-living fish. Very few 1+ group sandeels were present in food samples during the chick-rearing period.

2007 continued the recent trend for an increasing proportion of snake pipefish in the diet of several of the seabirds.

Highlights

  • Northern fulmar breeding success (0.21 chicks per incubating pair), which, with 2004, was the joint worst season on record.
  • European shags began breeding earlier than in 2006 and had a productive season. Shag was the only species for which productivity (1.07 chicks per pair) was above the long-term mean. Following high mortality during the winter, return rate at 60.8% took a drop from 2006 and was well below the long-term mean. As in the previous two years, the prey eaten was unusually varied with sandeels making up only 28.3% by mass of the diet, the lowest proportion on record. All sandeels that were recorded during chick-rearing were from older (1+ group) fish.
  • Black-legged kittiwakes had a very poor breeding season with productivity (0.24 chicks per completed nest) the lowest since 1999 and well below the long-term average. Adult return rate (62.9%) was the lowest on record. The proportion of sandeel in the diet (48% by biomass) was also the lowest recorded.
  • Common guillemots had their poorest breeding season on record with 0.28 chicks leaving per pair laying. The last four seasons have seen the three lowest breeding successes on record. As in the previous three years, many chicks were left unattended. Surprisingly, fewer were taken by gulls than killed by other guillemots and razorbills. Return rate of adults (75.2%) was also the lowest on record. Adults fed their chicks mainly on sprats with small gadoids the main alternative. Sandeels made up only 1% of the diet by mass. Chicks grew slowly and all the evidence suggested that feeding conditions were poor.
  • Razorbill breeding was earlier than last year and, in contrast to most other species, breeding success (0.63 chicks leaving per pair) was close to the long-term average. Adult return rate (80.0%) was also close to the long-term average. Chicks were fed mainly 0-group sandeels.
  • Atlantic puffins had their worst ever breeding season at 0.29 chicks per pair, which is a huge drop on the previous lowest figure. Unprecedented rainfall washed out numerous burrows and those chicks which managed to survive the wet conditions showed slow growth rates and high mortality. Return rate for adults (56.9%) was also the lowest on record. Chicks were mainly fed 0-group sandeels (82% by number, 76% by biomass).

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Top photo: Puffins on the Isle of May. Photo: Gwyen Rees/CEH