Body condition of stranded Razorbills and Atlantic Puffins in the Western Mediterranean

Abstract

Annual mass migrations of seabirds between their breeding and wintering grounds are critical for ensuring their survival and reproductive success. It is essential to comprehend their physical condition in order to identify the causes of death and to facilitate conservation efforts. This study focuses on evaluating the age, body condition index, and metabolites in liver and muscle (triglycerides, glycerol, glycogen, cholesterol, lactate, and glucose) of stranded Razorbills (n = 84) and Atlantic puffins (n = 11). The study was conducted along the Andalusian coast of Spain during the winter season of 2022-2023. The study examined the body condition of stranded individuals and their metabolic state to determine potential factors that may have caused their deaths. The study found that the majority of stranded individuals were juveniles. Both species exhibited low levels of carbohydrate (glucose and glycogen) in their tissues and high levels of lactate in their muscles. These findings could suggest that the individuals had undergone prolonged, strenuous exercise, demanding energy on anaerobic pathways, which may have been associated with migration. The study highlights the significance of adhering to standardized protocols when assessing the body condition of stranded seabirds. Doing so can help to identify causes of death and facilitate conservation efforts. A proposed index for body condition, which incorporates biometric measurements and individual physical condition, provides a comprehensive means of understanding the health of these unique species. This study underscores the importance of further research into the conservation measures and recommendations for protecting seabird populations. It is critical to comprehend the contributing factors of mass mortality incidents to work towards safeguarding these species and preserving their vital migration patterns.

Keywords: body condition assessment; conservation; mass die‐off events; metabolic analysis; stranded seabird.

FIGURE 1

Study area of the seabirds' collection (marked with the dashed orange line). Dots indicate sample sizes in each area. Data were collected from November 2022 to March 2023.

FIGURE 2

PCA for Razorbill: Variable Distribution and Relationships. The axes represent the principal components, with captures the most variance in the data. Red lines represent the relationship of each variable to the principal components. Quadrants indicate the relationship between observations and principal components. (0–4) positive influence on directions, (0–4) negative influence on directions.

FIGURE 3

Violin plots of Body Condition Index (calculated using wing length, body mass, subcutaneous fat, internal fat, and pectoral muscle) in Razorbill (n = 76) and Atlantic puffin (n = 10). The black line is the mean of body condition, and the width of the violin represents the sample size.

FIGURE 4

Bar plots of tissue metabolic condition of muscle and liver of Razorbill (a,b; n = 76) and Atlantic puffin (c,d; n = 10). mM/g w.w (millimoles/grams of wet weight). The bar represents the standard deviation.

FIGURE 5

Bar plots of tissue metabolic condition of muscle and liver of Razorbill (n = 76) and Atlantic puffin (n = 10). mM/g w.w (millimoles/grams of wet weight).The bar represents the standard deviation.

FIGURE 6

Bar plots of tissue metabolic condition of muscle and liver between juvenile (n = 57) and adult (n = 8) individuals of Razorbill. mM/g w.w (millimoles/grams of wet weight).The bar represents the standard deviation.

FIGURE 7

Bar plots of tissue metabolic condition of muscle and liver between juvenile (n = 6) and adult (n = 3) individuals of Atlantic puffin. mM/g w.w (millimoles/grams of wet weight).The bar represents the standard deviation.

FIGURE 8

Global distribution of registered areas with strandings and necropsied Razorbill (blue line), Atlantic puffin (orange line), and our study area (red line).