Early evidence of natal-habitat preference: Juvenile loons feed on natal-like lakes after fledging

Abstract

Many species show natal habitat preference induction (NHPI), a behavior in which young adults select habitats similar to those in which they were raised. However, we know little about how NHPI develops in natural systems. Here, we tested for NHPI in juvenile common loons (Gavia immer) that foraged on lakes in the vicinity of their natal lake after fledging. Juveniles visited lakes similar in pH to their natal lakes, and this significant effect persisted after controlling for spatial autocorrelation. On the other hand, juveniles showed no preference for foraging lakes of similar size to their natal one. When lakes were assigned to discrete classes based on size, depth, visibility, and trophic complexity, both juveniles from large lakes and small lakes preferred to visit large, trophically diverse lakes, which contained abundant food. Our results contrast with earlier findings, which show strict preference for lakes similar in size to the natal lake among young adults seeking to settle on a breeding lake. We suggest that NHPI is relaxed for juveniles, presumably because they select lakes that optimize short-term survival and growth. By characterizing NHPI during a poorly studied life stage, this study illustrates that NHPI can take different forms at different life stages.

Keywords: NHPI; habitat selection; juveniles; loons; natal habitat preference induction.

FIGURE 1

Two juvenile loons rest on Muskellunge Lake in Lincoln County, WI, showing color leg bands used for identification. (Photograph: Linda Grenzer)

FIGURE 2

(a) Study area in northern Wisconsin, in which 120 lakes are monitored across approximately 3,500 km². Shaded region in inset depicts breeding range of common loons in Wisconsin, and rectangle in inset depicts the approximate study region. Blue triangles depict lakes where nonresident juvenile loons visited in 2012–2015 (e.g., “Destination lakes”). Red squares depict lakes where the juvenile loons in the study originated from (“Natal lakes”). Black circles depict lakes that served as both destination and natal lakes. (b) Polar plot depicting the bearings and distances that juvenile loons traveled when leaving their natal lake. (c) Frequency distribution of the distances juvenile loons traveled between their natal and destination lakes (max = 33 km; mean = 7.5 km)

FIGURE 3

Randomization tests depicting the observed mean differences in lake variables between natal and destination lakes (solid black line) and the distribution of mean differences computed from a resampling simulation (dotted lines depict 95% confidence intervals). (a) Juvenile loons (n = 85) showed a significant tendency to visit lakes that are more similar in pH to their natal lake than would be randomly expected. (b) When data are subset into only those loon visits occurring within distances potentially affected by spatial autocorrelation (22 km; n = 77), juvenile loons exhibit a reduced yet significant likelihood of visiting lakes significantly more similar in lake pH than would be randomly expected

FIGURE 4

Distribution of lake visits from juvenile loons raised in either Complex lakes (light gray) or Simple lakes (dark gray). Irrespective of natal lake origin, all juveniles visits exhibited a significant preference for visiting destination lakes of Complex classes (Complex Lakes: X ² = 81.93. df = 5, p < 0.0001)

FIGURE 5

The proportion of juvenile loons visiting different lake types relative to their own natal lake class. Juvenile loons originating from Cool‐Complex‐Clear (CCC) lakes, Cool‐Complex‐Dark (CCD) lakes and Two‐Story (TS) lakes visited their own lake classes in greater proportions than would be expected given the background distribution of lake classes (CCC: X ² = 81.93. df = 6, p < 0.0001; CCD: X ² = 39.81, df = 6, p < 0.0001; TS: X ² = 49.96, df = 6, p < 0.0001). Other designations include Complex‐Warm‐Clear (CWC) lakes, Simple‐Cool‐Clear (SCC) lakes, Simple‐Cool‐Dark (SCD) lakes, and Simple‐Warm‐Dark (SWD) lakes