Daytime and nighttime activity at a breeding colony of Great Blue Herons in a nontidal environment

Abstract

MCNEIL, R., BENOPT, R., and DESGRANGES, J.-L. 1993. Daytime and nighttime activity at a breeding colony of Great BlueHerons in a nontidal environment. Can. J. Zool. 71: 1075 -1078. It is generally admitted that in coastal areas, herons of the genus Ardea adjust their foraging time according to the tidal cycle. However, to what extent do tides control the herons' daily rhythm of activity? To answer this question, we present the day and night activity patterns of Great Blue Herons (Ardea herodias) arriving to feed their young at a heronry located in a nontidal environment in southern Quebec. Herons were about half as active at night as during the day. Therefore, although significantly less than diurnal activity, nocturnal activity was not negligible, and consequently the tide cycle is not the only factor controlling the daily rhythm of the herons' activity. Those breeding pairs that were most active during the day were no more or less active at night. Diurnal activity was more closely correlated with the number of young that fledged than was nocturnal activity. Thus, night activity was not necessarily important for the survival of young herons, but it could be explained by other factors such as the greater availability of certain prey at night. MCNEIL, R., BENO~T, R., et DESGRANGES, J.-L. 1993. Daytime and nighttime activity at a breeding colony of Great BlueHerons in a nontidal environment. Can. J. Zool. 71 : 1075 -1078. I1 est generalement admis que les herons du genre Ardea ajustent leurs periodes d'alimentation selon le cycle des marees dans les regions catikres. Cependant, jusqu'a quel point les marees contralent-elles le cycle d'activite des herons? Pour repondre a cette question, nous presentons les patrons d'activite diurne et nocturne de Grands Herons (Ardea Iterodias) revenant a leur nid pour nourrir leurs jeunes dans une colonie du sud du Quebec, situee dans un milieu non soumis a l'action des marees. Les herons ont Ct C moitik aussi actifs la nuit que le jour. Quoique significativement inferieure a l'activiti diurne, I'activite nocturne n'a donc pas kt6 negligeable et, en consequence, le cycle des marees n'est pas le seul facteur a contraler le cycle journalier d'activiti des herons. Les couples les plus actifs de jour n'ont kt6 ni plus ni moins actifs de nuit. L'activite diurne a semble avoir une influence plus grande que I'activite nocturne sur le nombre de jeunes a I'envol. L'activite diurne n'a donc pas Ct C particulikrement importante pour la survie des jeunes, mais elle peut s'expliquer par d'autres facteurs, tels la plus grande disponibiliti de certaines proies la nuit.

Importance of Proximity to Foraging Areas for the Pacific Great Blue Heron (Ardea herodias fannini) Nesting in a Developed Landscape

“…Black and Collopy (1982) found that Great Blue Herons in northern Florida used feeding sites to a greater extent at night. In contrast to activity in coastal marine environments, which is related to tidal movement, nocturnal activity of Great Blue Herons in interior areas such as rivers and lakes may be related to activity patterns of fish (McNeil et al 1993). McNeil et al (1993) found that total diurnal and nocturnal arrivals were more numerous at sunrise and sunset.…”

“…In contrast to activity in coastal marine environments, which is related to tidal movement, nocturnal activity of Great Blue Herons in interior areas such as rivers and lakes may be related to activity patterns of fish (McNeil et al 1993). McNeil et al (1993) found that total diurnal and nocturnal arrivals were more numerous at sunrise and sunset. Daytime activity (i.e., movement) was greater after 14 June, probably because young herons require more and more food as they mature, and activity was greater in nesting pairs with large broods.…”

Time‐integrated habitat availability is a resource attribute that informs patterns of use in intertidal areas

“…), and therefore, it is possible that nighttime feeding affects feeding patterns at other times (McNeil et al. ). Our simplifying assumption was that resource selection during the daytime was independent of resource selection during the nighttime.…”

“…Previous nighttime surveys of foraging Great Blue Herons (A. herodias) indicate that nighttime foraging does occur (Black andCollopy 1982, Powell 1987), but we could not quantify this effort because surveys were limited to the daytime. Daytime vs. nighttime foraging abundance differs markedly in some species of water birds (Robert et al 1989), and therefore, it is possible that nighttime feeding affects feeding patterns at other times (McNeil et al 1993). Our simplifying assumption was that resource selection during the daytime was independent of resource selection during the nighttime.…”

Great Blue Heron Predation on Stocked Rainbow Trout in an Arkansas Tailwater Fishery

“…Great blue herons may forage nocturnally (Brandman 1976;Black and Collopy 1982;Rojas et al 1999), but due to visibility constraints we could only identify prey and estimate the size of prey during daylight hours. Diel patterns have been observed in a number of fish species (e.g., Sjö berg 1989; Heggenes et al 1993), so shifts in prey availability could alter great blue heron diets where nocturnal foraging occurs (McNeil et al 1993). The nocturnal foraging patterns among great blue herons are varied; in some systems the rate of nocturnal foraging activity is equal to the rate of diurnal foraging activity (Black and Collopy 1982), while in other systems nocturnal foraging in great blue herons is absent (Gawlik 2002).…”