Mark Cook - Academia.edu (original) (raw)

Papers by Mark Cook

Behavioral Ecology, Mar 1, 2004

Competitive interactions among siblings are an important determinant of parental fitness. These a... more Competitive interactions among siblings are an important determinant of parental fitness. These are strongly influenced by relative offspring size and therefore also by the extent to which parents can influence offspring size hierarchies. The temporal pattern of hatching in an avian clutch has a large effect on size and developmental disparities among chicks. Hatching spread is generally assumed to be mainly determined by the onset of incubation in relation to egg laying. However, the extent to which factors other than incubation onset, such as development rate, also influence timing of hatching has received little empirical investigation. We compared incubation periods of male and female black guillemot (Cepphus grylle) embryos to ascertain whether the time taken for an egg to hatch varies with embryo sex. Laying date and egg mass had no significant effect on incubation time, but male embryos hatched on average a day sooner than did females. The onset of incubation and hatching spread vary in black guillemots. However, in mixed-sexed clutches in which the first-laid embryo is male, a faster development time of males should mean asynchronous hatching regardless of parental incubation regime. This was supported by empirical investigation. These results demonstrate that factors other than incubation behavior can be important in establishing avian hatching patterns. Whether these sex differences in development rate are a result of constraints on the degree of parental control, or an adaptive strategy to manipulate hatching patterns, remains to be established.

Journal of Avian Biology, 1997

Cook, M. I. and Hamer, K. C. 1997. Effects of supplementary feeding on provisioning and growth ra... more Cook, M. I. and Hamer, K. C. 1997. Effects of supplementary feeding on provisioning and growth rates of nestling Puffins Fratercula arctica: evidence for regulation of growth.-J. Avian Biol. 28: 56-62. We used a supplementary feeding experiment to investigate the existence of a causal relationship between the nutritional status of nestling Puffins and the subsequent rates of food provisioning by their parents. Chicks given supplementary food received less frequent meals than controls, with the effect that the total amount of food received by the experimental group (parental delivery plus supplementary food) was similar to the amount delivered by parents in the control group. This indicated compensatory regulation of provisioning by parents in the experimental group. Increases in body size and body mass were virtually identical in the two groups until shortly before fledging, when supplemented chicks attained higher body mass than controls. This difference appeared to result mainly from the fact that unmanipulated chicks normally receive little food from their parents towards the end of the nestling period; supplements thus constituted a large proportion of chicks' normal daily food intake over this period, and compensatory reduction in food delivery by parents did not completely match the extra food given to chicks in the supplemented group. If growth rates of chicks were usually limited by poor food supply and adults delivered food to the chick at the maximum rate permitted by food availability irrespective of the chick's immediate nutritional requirements, then regulation of food delivery by parents would not be expected. The fact that adults were regulating food delivery to their offspring below the maximum attainable rate suggests that in this study at least, nestling growth rate was not limited by a scarce and unpredictable food supply. M. I. Cook and K. C. Hamer (correspondence),

Ornithological Applications, 2021

As avian reproductive success is generally prey limited, identifying important prey types or size... more As avian reproductive success is generally prey limited, identifying important prey types or sizes and understanding mechanisms governing prey availability are important objectives for avian conservation ecology. Irruptive White Ibis (Eudocimus albus) nesting at coastal colonies in the southern Everglades numbered over 100,000 nests in the 1930s. A century of drainage and altered hydrologic patterns reduced aquatic prey availability and eliminated large nesting events; nesting activity in recent decades has been typically less than 5% of historical peaks. Hydrologic restoration is expected to increase ibis nesting activity, but which prey types will support high nesting effort is less clear. In 2017 and 2018, we collected food boluses from White Ibis chicks at coastal colonies in Everglades National Park. We also monitored regional nesting activity from 1999 to 2018. In 2017, the region had 1,075 nests, typical of the past several decades; but in 2018, there were 30,420 nests, repre...

The mechanisms causing native displacement by invasive species are challenging to identify. We us... more The mechanisms causing native displacement by invasive species are challenging to identify. We used survey data to demonstrate a local extinction of a native gastropod ( Pomacea paludosa ) from a Florida wetland coincident with invasion of a non-native gastropod ( P. maculata ). We then examined the potential for P. maculata to displace P. paludosa . We used two field experiments to examine effects of densities and heterospecific interactions on juvenile growth in situ and we used lab and mesocosm experiments to explore chemically-mediated interactions between the species. Field experiments produced variable results; evidence for reduced P. paludosa growth in the presence of P. maculata was found under higher nutrient conditions with fast snail growth rates, but growth inhibition disappeared under oligotrophic conditions. Resource reduction could not be demonstrated in the field. Juvenile P. paludosa did not avoid mucus of P. maculata and did not reduce feeding in response to cues. ...

I examined natural variation in the reproductive strategy of the black guillemot, with particular... more I examined natural variation in the reproductive strategy of the black guillemot, with particular emphasis on the consequences for nestlings. Data were collected from a population of c. 65 breeding pairs on the Holm of Papa Westray, northern Scotland. Temporal differences in reproductive strategy are likely to reveal the reproductive constraints most pertinent to a species, exhibit how reproductive costs are manifest, and highlight the potential trade-offs selected to maximise reproductive success in the face of such costs. Constraints appeared to operate both at the egg production and chick rearing stages, with annual and seasonal effects influencing egg size, chick growth and survival. However, females did not alter the allocation of resources between eggs, nor the degree of hatching asynchrony, suggesting that females maintained the level of competitive asymmetry within the brood, despite these constraints. The relationship between egg size and breeding success was investigated. ...

While Everglades restoration as related to phosphorus (P) has focused on reducing concentrations ... more While Everglades restoration as related to phosphorus (P) has focused on reducing concentrations and loads to the region via the implementation of the stormwater treatment areas (STAs), a significant portion of the Everglades ecosystem remains impacted with high levels of P, readily evidenced by over 11,000 ha of monotypic cattail (Typha domingensis) stands. This has resulted in considerable attention on removing cattail as a restoration method, despite the recognition that cattail removal is addressing the symptom as opposed to solving the problem. Large scale intensive restorations efforts (e.g. peat removal or adding chemical amendments) will likely be more disruptive and harmful to the Everglades landscape than allowing the system to recover naturally. Additionally, large-scale removal may be detrimental because the dense cattail areas adjacent to inflow points currently serve an important ecosystem function; protecting downstream pristine areas through their rapid growth and P removal. However, ecosystem function could be enhanced by recognizing the constraints inherent in a monotypic cattail community. That is, there may be some active management strategies that can be implemented in conjunction with a "natural recovery strategy" that may improve ecological function, and thereby contribute to the overall intent of Everglades restoration. A key constraint is the density of the vegetation resulting in net heterotrophic production and limited access by wildlife. Therefore, the first objective in this research project is to assess whether creating openings in dense cattail areas will sufficiently alter trophic dynamics such that wildlife diversity and abundance is increased. As the goal of restoration is to return the Everglades to predrainage conditions as much as possible, the second objective then becomes, to what extent does the structure and function of these created open areas compare to those of the natural Everglades. Combining the answers to these two questions will allow us to make recommendations on this active management strategy as a means to accelerate ecosystem recovery. Our fundamental hypothesis is that creating openings in P impacted landscapes will cause a shift from the emergent macrophyte-detrital system to one dominated by algae or submerged aquatic vegetation (SAV). In doing so, changes in critical ecosystem processes and food web dynamics will occur. Traditional approaches to examining ecological change can be characterized into two groups; one organism-centric (i.e., community ecology) and the other nutrient-centric (i.e., process level responses; Moore et al. 2004). The community approach emphasizes characteristics such as species composition, density, diversity, and population dynamics. Utilizing this approach in the Everglades, periphyton, macrophyte, and invertebrate communities have been shown to be significantly different in highly enriched densely vegetated areas compared to more open habitats of the unenriched sloughs (McCormick et al. 2001a). In contrast, taking a process level approach we have demonstrated that algal and plant productivity and P content increase in response to P enrichment (Miao and Sklar 1998, McCormick et al. Options for Accelerating Recovery of Phosphorus Impacted Areas of the Florida Everglades Research Plan 2001b), resulting in increased peat accumulation and P storage in the soil (Reddy et al. 1993, Craft and Richardson 1993, DeBusk et al. 2001). Both these approaches increase understanding of specific aspects of wetland structure and function, and the parameters we measure in this study will allow us to draw both community and process level interpretations of treatment differences. The relationships between food web interactions and nutrient supply are often traditionally studied under the guise of "bottom-up" and "top-down" forces. Within this framework, one way to assess how species interact is to measure changes in individual species density or community composition in response to a perturbation (e.g. nutrient enrichment or predator introduction). However, as pointed out by Elser et al. (1998) and Sterner and Elser (2002) these relationship are far more complex than the dichotomous view of "bottom-up" and "top-down". One factor that may account for this greater complexity is the quality of the food available for consumption. That is, consumer taxa may be constrained by the abiotic factors, biotic factors, and feedback mechanisms that regulate the nutrient status and elemental composition of autotrophs (Elser et al. 1998). Recently, multivariate experiments have shown that these patterns of interdependency also apply to ecosystem functions such as C and N storage (Worm et al. 2002). Because of this interdependency of community structure and ecosystem function, it is important to link nutrient supply and food web structure together. Using a stoichiometric approach, it is possible to couple traditional methods of assessing the food web (species composition and density) with the nutrient status and elemental composition of various components of the ecosystem to define food web dynamics.

Waterbirds, 2012

Wading bird (Ciconiiformes) nesting success is influenced by the availability of aquatic prey, bu... more Wading bird (Ciconiiformes) nesting success is influenced by the availability of aquatic prey, but principle prey may differ among species. During an excellent nesting year (2009) 118 boluses were collected from nestlings of three species, White Ibis (Eudocimus albus), Tricolored Heron (Egretta tricolor) and Snowy Egret (Egretta thula) in a mixed colony in the northern Everglades. Although these species have similar foraging depths and foraging flight distances from nesting colonies, crayfish dominated the ibis boluses while small-bodied fishes dominated egret boluses. Fish prey species composition in Snowy Egret and Tricolored Heron boluses did not differ. Compared to available fish species from nearby wetlands, the Egretta spp. did not exhibit taxonomic selectivity but did feed selectively on larger (2-4 cm standard length) fish. Whether restoration activities in the Everglades, including hydroperiod lengthening, will simultaneously enhance prey for both invertivores like White Ibis and piscivores, such as the egrets, remains an open question.

Ibis, 2011

Prey availability is known to limit reproduction of some species of nesting birds, but identifyin... more Prey availability is known to limit reproduction of some species of nesting birds, but identifying the primary prey types of a species with a flexible diet can be challenging. For the White Ibis Eudocimus albus, a tactile feeding, medium-sized wading bird, nestling prey composition is suggested to depend on landscape water depths ⁄ availability of foraging habitat at the time of nesting and on historical drying events affecting prey production. We collected and compared inter-and intra-annual diet variation of White Ibis chicks reared in the Everglades over two years that were independently identified as being relatively good (2006) and poor (2007) nesting seasons. We collected 127 nestling boluses and analysed the temporal variation in biomass of eight functional prey groups using multivariate techniques. The boluses from 2006 in the central Everglades were dominated by fish, but in 2007, after fish had been reduced by the previous year of drying, the boluses from the same region were more variable and dominated by garbage (i.e. scavenging). Analysis of five different collections taken from a different colony in the northern Everglades indicated that boluses were characterized by crayfish and had fewer fish or less garbage when landscape water depths were relatively higher and more preferred habitat was available. At lower landscape water depths in 2007 the bolus composition shifted away from crayfish towards small fish and urban food (terrestrial insects and garbage). Our results support the suggestion of depth-dependent diets; prey composition depends on the current landscape water levels around the colonies, and also suggests that previous drying events can lead to increased reliance on alternative food sources. White Ibis partially compensated for unavailable aquatic prey with alternative urban foods, but their nesting success appears to have suffered.

Functional Ecology, 2010

1. Physiological responses to environmental stress such as adrenocortical hormones and cellular s... more 1. Physiological responses to environmental stress such as adrenocortical hormones and cellular stress proteins have recently emerged as potentially powerful tools for investigating physiological effects of avian food limitation. However, little is known about the physiological stress responses of free-living nestling birds to environmental variation in food availability. 2. We experimentally tested how hydrologically mediated changes in food availability affect the physiological stress responses of juvenile white ibises Eudocimus albus in a fluctuating wetland. We provided supplementary food to free-living nestlings during 2 years with contrasting hydrologic and food availability conditions, and used plasma (PCORT) and faecal (FCORT) corticosterone and heat shock proteins (HSP60 and HSP70) from first-hatched (A-nestlings) and second-hatched (B-nestlings) to detect relatively short-to long-term responses to food limitation. 3. Nestling physiological stress responses were relatively low in all treatments during the year with optimal food availability, but PCORT, FCORT and HSP60 levels increased during the poor food year. FCORT and HSP60 responses were clearly due to nutritional condition as elevated concentrations were evident primarily in control nestlings. Significant year by hatch order interactions for both FCORT and HSP60 revealed that these increases were largely incurred by B-nestlings. FCORT and HSP60 responses were also well developed early in neonatal development and remained elevated for the duration of the experiment suggesting a chronic stress response. PCORT and HSP70 were less informative stress responses. 4. The nutritionally mediated increases in FCORT and HSP60 provide compelling evidence that white ibis nestlings can be physiologically affected by environmental food levels. FCORT and HSP60 are effective indicators of nutritional mediated stress for nestling white ibises and potentially for other species prone to capture or handling stress.

Ecology, 2005

Avian parents influence the onset of development, hatching synchrony, and likelihood of brood red... more Avian parents influence the onset of development, hatching synchrony, and likelihood of brood reduction through the onset of incubation. Studies testing adaptive functions of brood reduction assume that eggs are protected by their shells and waiting for parents to initiate incubation in a manner that creates optimal hatching patterns, but the viability of early laid eggs may diminish over time due to putative effects of ambient temperature. We tested effects of exposure to ambient temperature on the viability of unincubated bird eggs using an altitudinal climate gradient in Puerto Rico: daily maximum temperatures nearly always exceed developmental zero in the lowland forest, whereas temperatures rarely exceed developmental zero in the cloud forest and at intermediate altitudes. We removed 382 freshly laid Pearly-eyed Thrasher (Margarops fuscatus) eggs, placed them in holding boxes at three sites for 1-7 days, and returned them to nests to be incubated. Additional control eggs (n ϭ 39) tested effects of both handling and movement on hatching success, and unmanipulated eggs (n ϭ 139) provided a measure of natural hatching success. Hatching success of control eggs (82.0%) and unmanipulated eggs (84.9%) did not differ, indicating no impacts of handling on hatchability. Hatching success of experimental eggs exposed for one day (78.6%) was high but declined very strongly after exposure for three days (41.9%), five days (11.5%) and seven days (2.1%). Hatchability of eggs held at the cloud forest did not differ from eggs held at the lowland site but was lower for eggs exposed at mid-elevation. Hatching success was positively related to minimum temperature and marginally related to mean temperature and proportion of time above developmental zero. Exposure duration, treatment site, and maximum temperature were the only significant effects identified by stepwise logistic regression. Eggs held at the lowland site had shorter developmental periods than eggs held at other sites. Most embryo mortality (80.8%) occurred at very early stages. Our results demonstrate that viability of unincubated eggs exposed to moist tropical conditions declines strongly but suggest that ambient temperature is not the sole cause. We compare rates of egg viability decline among species, examine alternative mechanisms for the loss of viability, and discuss the significance of egg viability on avian life histories.

Ecological Indicators, 2014

In our companion manuscript we identified 11 waterbirds as indicators of various pressures on the... more In our companion manuscript we identified 11 waterbirds as indicators of various pressures on the coastal marine ecosystems of southern Florida. Here, we identify the habitats on which these species depend and the ecological linkages that make them representative of those habitats. Through the use of conceptual ecological models (CEMs), we develop tools that can be used by managers/decision makers to evaluate the health of the various habitats in order to rectify myriad problems that are occurring or will possibly occur in the future such that the valuable ecosystem services provided by these habitats can be maximized. We also demonstrate the practical use of these tools by documenting data availability, benchmarks, and scientific needs for each species.

The Condor, 2010

Resumen. El forrajeo exitoso de las aves depredadoras es influenciado de forma importante por la ... more Resumen. El forrajeo exitoso de las aves depredadoras es influenciado de forma importante por la disponibilidad de presas, la cual no sólo comprende la densidad de las presas sino también su vulnerabilidad a ser capturadas. Se cree que ciertas características del hábitat como la profundidad del agua y la densidad de la vegetación afectan la vulnerabilidad de las presas acuáticas de las aves vadeadoras (Ciconiiformes). Para determinar sus efectos sobre la selección del hábitat de alimentación y el éxito de forrajeo de las aves vadeadoras, manipulamos experimentalmente la profundidad del agua y la densidad de la vegetación acuática sumergida (VAS) en áreas cercadas (10 10 m) con densidades iguales de peces en enero y abril de 2007. Nuestros análisis de los resultados con el índice de selección de Manly mostraron que las aves vadeadoras prefirieron ambientes con aguas someras y VAS. Sin embargo, los dos componentes del hábitat tuvieron efectos débiles sobre el éxito de forrajeo de las aves, pues la tasa de captura no varió con la profundidad ni con la densidad de la VAS. La eficiencia de captura no varió con respecto a la densidad de la VAS y, de hecho, fue menor en aguas someras, un resultado contrario a lo que esperábamos. Nuestros resultados sugieren que las aves seleccionaron el hábitat con base en señales ambientales como la profundidad del agua y la VAS, pero esos factores no afectaron al éxito de forrajeo fuertemente. Planteamos la hipótesis de que las aves vadeadoras estaban seleccionando ambientes con aguas someras y VAS debido a que anticipaban un beneficio relacionado con el forrajeo mediante niveles mayores de densidad y vulnerabilidad de las presas. Sin embargo, la densidad relativamente alta y uniforme de las presas ubicadas en las áreas cercadas, así como la escala de estas áreas, efectivamente condujeron a igualar la vulnerabilidad de las presas entre los tratamientos.

The studies and findings discussed in this chapter of the 2007 South Florida Environmental Report... more The studies and findings discussed in this chapter of the 2007 South Florida Environmental Report-Volume I are presented within four main fields: (1) wildlife ecology, (2) plant ecology, (3) ecosystem ecology, and (4) landscape ecology. Table 6-1 provides a summary of current Everglades research in relation to objectives, operational mandates, and restoration performance measures. Programs of study were based on the short-term operational needs and long-term restoration goals of the South Florida Water Management District (SFWMD or District) including large-scale and regional hydrologic needs in relation to regulation schedules, permitting, the Everglades Forever Act mandates, and the Comprehensive Everglades Restoration Plan.

Behavioral Ecology, 2000

Siblings in a diversity of species are facultatively aggressive, yet the proximate control of the... more Siblings in a diversity of species are facultatively aggressive, yet the proximate control of the aggressive response and the ecological conditions selecting for such systems are poorly understood. In this study, we investigated the effects of food amount (food amount hypothesis) and competitive asymmetry on sibling aggression in black guillemot broods. Parental provisioning rates were experimentally manipulated in broods comprising a range of hatching intervals over a 12-h period. Aggression became evident only after parental provisioning rates were experimentally reduced. When parental provisioning resumed, adults did not increase their feeding rate to compensate for the induced food deficit, and the result of sibling rivalry was a change in the allocation of parental deliveries from one of equality to one in favor of the dominant chick. Food-deprived chicks from synchronous broods were more aggressive than those from asynchronous broods, suggesting that one benefit of hatching asynchrony in the black guillemot is to establish an efficient competitive hierarchy among siblings which minimizes the need for costly aggressive interactions. On the following day, sibling aggression ceased, and chicks regained an equal share of parental feeds. Our results provide the first evidence that short-term food shortage per se acts as an initial trigger for aggression and also show that the aggressive response is complicated by factors associated with hatching and laying order.

Behavioral Ecology, 2004

Ecological Indicators, 2009

Ecology Letters, 2005

Avian eggshells harbour microbes shortly after laying, and under appropriate ambient conditions t... more Avian eggshells harbour microbes shortly after laying, and under appropriate ambient conditions they can multiply rapidly, penetrate through shell pores, infect egg contents and cause embryo mortality. We experimentally examined how incubation affects bacterial processes on the eggshells of pearl-eyed thrashers Margarops fuscatus nesting in tropical montane and lowland forests in Puerto Rico. Bacteria and fungi grew rapidly on shells of newly laid, unincubated eggs exposed to ambient conditions, but declined to low levels on shells of eggs incubated by thrashers. Divergence in bacterial growth between incubated and exposed eggs was more marked at the montane forest than at the lowland site. Pathogenic microorganisms became increasingly dominant on shells of exposed eggs, but these groups were relatively rare on incubated eggs, where more benign, less invasive groups prevailed. Some incubation during laying may be necessary to decrease the probability of trans-shell infection by reducing the growth of harmful bacteria and fungi on eggshells, although it may increase hatching asynchrony and the likelihood of brood reduction.