**2.3 The case of the white stork**

*Birds - Challenges and Opportunities for Business, Conservation and Research*

that produced 450 young.

such as wetlands.

affect aquatic vegetation ..." (**Figure 11**).

something that cannot be seen from the shores.

Its presence was relatively scarce until the end of the nineties, with colonies in the Pétrola lagoon, in the province of Albacete. In 2010, a breeding colony was installed in the Manjavacas lagoon (Cuenca), with a total of 2,500 adult specimens

According to [25]: "Physical alterations are evident in the case of the greater flamingo which is one of its forms of feeding behavior, leaves obvious craters of approximately one meter in diameter at the bottom of the wetlands it occupies. This modification of the sediment topography, in addition to hydrological changes, can

An important opinion indicates [15]: "the density of flamingos has doubled several times in Spanish wetlands, due to the combination of species management (including measures to ensure nesting more frequently than would be natural for this species) and the destruction of many wetlands used outside the breeding season. The destruction of submerged macrophyte meadows by flamingoes, harms ducks, coots (*Fulica atra, F. cristata*) and other birds that depend on them, but may favor waders that prefer to feed in open water areas [12]. In part, this could explain the positive correlation between the abundance of flamingos and waders".

The case of the flamingo is another example of management, in favor of a species, that has overflowed, causing enormous damage to especially fragile ecosystems

It has never been a real endangered species. The interconnection between the Mediterranean and Northwest African colonies has been ensuring their survival and causing their overpopulation. This is another wrong case of "the more the merrier". Intervention is essential to limit the population of this species and to do it very soon.

*Flamingos leave obvious craters of approximately one meter in diameter at the bottom of the wetlands it* 

The increase in the density of the greater flamingo in Spain, and the Mediterranean area, is higher than what has been announced. The destruction of lagoons by the excessive number of flamingos is an indisputable fact, but it goes unnoticed. The turbidity of the waters after the flamingo flocks' search for food is

**102**

**Figure 11.**

*occupies. Photo J. Porrero.*

The white stork population in Spain decreased notably in the second third of the 20th century, after the closure of landfills in small rural towns, the centralization of waste treatment at the county level and, most likely, due to the increased use of Organochlorine insecticides such as DDT, which decreased the number of invertebrates in the field and could affect the fertility of storks.

The 1984 census of nesting pairs was 6,753 nests, with a decrease of 8% concerning the 1974 census and 47% regarding the 1957 census [26, 27]. Starting in 1984, the population grew again at a good pace, reaching the figure of 16,643 in the 1994 census, which meant a percentage increase of 146% [28]. There was a new increase in the 2004 census, reaching 33,217 breeding pairs: population growth of 100% (**Figure 12**) [29].

The changes produced in agricultural land, the use of insecticides and herbicides, the intensification of crops, the disappearance of puddles and small wetlands, have caused a change in the behavior of storks, at least in the province of Badajoz, both in their methods and places of hunting as in the specific object of their diet [3, 5].

There is an increase in the density of the white stork population in the province of Badajoz, coinciding with the figures from the censuses. A large part of that population no longer migrates. It remains in its breeding territories all year round. Winters are milder, due to climate change, and you have food

**Figure 12.** *Stork chicks just fed by the adult. Photo. M. Calderón.*

#### **Figure 13.**

*A decade ago this would be a flock of premigratory storks, now it is a pre-wintering flock. Photo M. Calderón.*

resources at your fingertips, so you neither need nor compensate for migration to Africa (**Figure 13**) [3, 5].

The white stork hunting system is solitary during the breeding season. During the migratory season, and in winter, in their African territories, the group hunt in line, beating fields in search of prey [30].

As many specimens remain in Extremadura during the winter, without migrating, they use the same hunting technique as in Africa. In the La Serena area, it is common to observe, in recent years, groups of 40–60 storks in a line, advancing in unison, capturing any animal that moves in their path.

This hunting system - it is being observed - they have begun to use it also in the breeding season. In previous years, storks hunted in cereal crops, until the plants reached a height like their tarsi, not returning till after harvest.

Currently, they have been observed hunting, among wheat or barley plantations that exceed their height, to the point that they already dare to prey on Montagu's harrier young which they capture directly in the nests of this raptor located on the ground [3]. It is another proof of the stork's change in feeding strategy. Previously, it had been observed preying on the nests of smaller birds, such as the lark (*Alauda arvensis)* and, exceptionally, house sparrow adults (*Passer domesticus/hispaniolensis*) that install their nests in the vicinity of the white stork nests [5].

These new predatory behaviors may be due to the scarcity of common prey (Orthoptera, Coleoptera, amphibians and reptiles), being forced to increase the spectrum of prey.

The increase in the density of storks in Extremadura, due to various causes in which man has always intervened, has caused an ecological problem of great importance but truly little visible: it is the enormous decrease in amphibians and reptiles, even when they keep in the small ponds in which the first ones reproduce. The constant predatory pressure of white storks on amphibians in humid areas, which are rare in the region, has led to the virtual extinction of these groups, with no specimens being observed or heard in areas where, until about 7 or 8 years ago, were relatively abundant (**Figure 14**).

As an example, a case followed in detail: This is a section of the Ortigas river as it passes through the municipality of La Guarda (Badajoz).

**105**

*The Limit to the Density of Species (A Reflection on Human Intervention in Conservation...*

Until 2012, there was a variable number in that stretch of the river, 9 stork nests in the trees of the river and 3–5 on the roof of the village church. In spring and summer, the nocturnal songs of toads, toads and frogs were heard, according to their different periods. In 2014 another colony of storks was installed with 8 new nests.

A quick and reliable way of dating the abundance of reptiles and amphibians in that area was to travel a 6 km stretch of the road that connects the town of La Guarda with Campanario (10 km.), With little traffic of vehicles during the day, and width of 5 m, noting the snakes run over and those that cross from one side to the other (*Malpolon monspesulanus, Zamenis scalaris*). Upon return, several stops were made to observe, at different preset stations, the density of ocellated lizards

The same road can serve as a measurement and sampling unit for the density calculations of some amphibians (*Epidalea calamita, Pelobates cultripes).* To do this, a night in April had to be chosen, after a rainy day. The transit of amphibians between small ponds, in search of a mate, reached such densities that, in some sections, it was impossible to continue driving, being necessary to travel the road on foot, so as not to kill dozens of amphibians by crushing [31]. Some data for the years 1973–1990 reached 3 snakes/km and 20 amphibians/km, with some concentration

At present, with a somewhat higher frequency of passage of cars, the finding of a snake run over is anecdotal, and the passage of amphibians is imperceptible or

the species that make it up. An increase in predators means a decrease in prey. When the number of predators is excessive, the usual prey disappears, being

a lack of studies that quantify it, urgently, so as not to be too late, as usual …

disappearance of amphibians and reptiles in surrounding areas.

The trophic chain must be conserved based on the proportional balance between

replaced by others that are not prepared for the new threat, entering a disadvantage. In the case of the white stork, its predation, in such high numbers, is causing the

This situation could be extrapolated to the rest of the Spanish territory. There is

Since that year, the silence of the amphibians is permanent.

(*Timon lepidus*.) in the rocky areas near the road [31].

points of 78 amphibians/100 m.

non-existent.

**Figure 14.**

*Stork hunting alone. Photo M. Calderón.*

*DOI: http://dx.doi.org/10.5772/intechopen.97436*

*The Limit to the Density of Species (A Reflection on Human Intervention in Conservation... DOI: http://dx.doi.org/10.5772/intechopen.97436*

**Figure 14.** *Stork hunting alone. Photo M. Calderón.*

*Birds - Challenges and Opportunities for Business, Conservation and Research*

resources at your fingertips, so you neither need nor compensate for migration to

*A decade ago this would be a flock of premigratory storks, now it is a pre-wintering flock. Photo M. Calderón.*

The white stork hunting system is solitary during the breeding season. During the migratory season, and in winter, in their African territories, the group hunt in

As many specimens remain in Extremadura during the winter, without migrating, they use the same hunting technique as in Africa. In the La Serena area, it is common to observe, in recent years, groups of 40–60 storks in a line, advancing in

This hunting system - it is being observed - they have begun to use it also in the breeding season. In previous years, storks hunted in cereal crops, until the plants

Currently, they have been observed hunting, among wheat or barley plantations that exceed their height, to the point that they already dare to prey on Montagu's harrier young which they capture directly in the nests of this raptor located on the ground [3]. It is another proof of the stork's change in feeding strategy. Previously, it had been observed preying on the nests of smaller birds, such as the lark (*Alauda arvensis)* and, exceptionally, house sparrow adults (*Passer domesticus/hispaniolensis*)

These new predatory behaviors may be due to the scarcity of common prey (Orthoptera, Coleoptera, amphibians and reptiles), being forced to increase the

The increase in the density of storks in Extremadura, due to various causes in which man has always intervened, has caused an ecological problem of great importance but truly little visible: it is the enormous decrease in amphibians and reptiles, even when they keep in the small ponds in which the first ones reproduce. The constant predatory pressure of white storks on amphibians in humid areas, which are rare in the region, has led to the virtual extinction of these groups, with no specimens being observed or heard in areas where, until about 7 or 8 years ago,

As an example, a case followed in detail: This is a section of the Ortigas river as it

Africa (**Figure 13**) [3, 5].

**Figure 13.**

line, beating fields in search of prey [30].

unison, capturing any animal that moves in their path.

reached a height like their tarsi, not returning till after harvest.

that install their nests in the vicinity of the white stork nests [5].

**104**

spectrum of prey.

were relatively abundant (**Figure 14**).

passes through the municipality of La Guarda (Badajoz).

Until 2012, there was a variable number in that stretch of the river, 9 stork nests in the trees of the river and 3–5 on the roof of the village church. In spring and summer, the nocturnal songs of toads, toads and frogs were heard, according to their different periods. In 2014 another colony of storks was installed with 8 new nests. Since that year, the silence of the amphibians is permanent.

A quick and reliable way of dating the abundance of reptiles and amphibians in that area was to travel a 6 km stretch of the road that connects the town of La Guarda with Campanario (10 km.), With little traffic of vehicles during the day, and width of 5 m, noting the snakes run over and those that cross from one side to the other (*Malpolon monspesulanus, Zamenis scalaris*). Upon return, several stops were made to observe, at different preset stations, the density of ocellated lizards (*Timon lepidus*.) in the rocky areas near the road [31].

The same road can serve as a measurement and sampling unit for the density calculations of some amphibians (*Epidalea calamita, Pelobates cultripes).* To do this, a night in April had to be chosen, after a rainy day. The transit of amphibians between small ponds, in search of a mate, reached such densities that, in some sections, it was impossible to continue driving, being necessary to travel the road on foot, so as not to kill dozens of amphibians by crushing [31]. Some data for the years 1973–1990 reached 3 snakes/km and 20 amphibians/km, with some concentration points of 78 amphibians/100 m.

At present, with a somewhat higher frequency of passage of cars, the finding of a snake run over is anecdotal, and the passage of amphibians is imperceptible or non-existent.

The trophic chain must be conserved based on the proportional balance between the species that make it up. An increase in predators means a decrease in prey. When the number of predators is excessive, the usual prey disappears, being replaced by others that are not prepared for the new threat, entering a disadvantage. In the case of the white stork, its predation, in such high numbers, is causing the disappearance of amphibians and reptiles in surrounding areas.

This situation could be extrapolated to the rest of the Spanish territory. There is a lack of studies that quantify it, urgently, so as not to be too late, as usual …

**Figure 15.** *Cattle heron on a sheep. Photo F. del Río.*
