The Garraf is an antidote to claustrophobic canyons, which is how Barcelona’s streets sometimes feel. It’s an airy expanse of garrigue-covered hills, open to the shining sea. We didn’t have to go far to find the Two-tailed Pasha (Charaxes jasius), top on Lisa and Teresa’s list along with the Autumn narcissus (Narcissus serotinus). While the Pashas chased each other around the fig trees near the visitors’ centre, Lisa and Teresa stalked them with their cameras.

Meanwhile, Nick and I followed a signposted botanical route, an excellent way to learn some of the plant species typical of the area: Kermes oak, Prickly juniper, and cistus. Nick spotted a solitary white flower, fragile among all the tough leathery leaves and spines. It was photographed and duly forgotten. We also discovered that the Garraf strawberry trees (Arbutus unedo) produce some of the best arbutus cherries anywhere: sweet and acidic, unlike the bland fruit I’d tasted before. They clearly thrive on this sun-soaked limestone terrain.

The lonely white flower did turn out to be an Autumn narcissus, as was discovered much later in the car. It was too late to turn back, but Teresa forgave us and continued to share her extensive knowledge. So we were able to learn that the Tree heath (Erica arborea) familiar to everyone who walks in Collserola only grows in acidic soil, and here is replaced by the purple-flowering Mediterranean heath (Erica multiflora). An insect slipping its black segments across the fallen pine needles turned out to be a Glow worm larva (Lampyris noctiluca), with a voracious appetite for snails. A dirty clump of debris hanging on a guardrail was identified as the case of a Bagworm.

After some debate, we decided there was time for the Llobregat Delta. Back down at sea level and just after the turn-off for the reserve, something white caught our eye: an extensive patch of Autumn Narcissi.

After liberal applications of mosquito repellent and an osprey-sighting, we crossed the bridge into the reserve. Outside the hides, translucent herons fished in sparkling water, sandpipers bathed in the shallows, cattle egrets groomed the horses, kingfishers streaked here and there, and spoonbills tried to keep up with their restless spatula-shaped bills.

There was little time left, but Collserola could not be missed. Up by the Forat del Vent, suitably windy, a flock of Pekin robins (Leiothrix lutea) held our attention with their melodious Blackcap-like song. Unlike other exotic escapees that settle in more urban environments, these South Asian cage birds are breeding in woodlands. They’re being monitored but studies suggest their presence has so far had no harmful effect on the authoctonous species.

We’d run out of daylight. After dropping Nick and I off at the metro, Lisa and Teresa drove away for the next stage of their adventure.

We were lucky to stumble on it, as they’re not common in Collserola. Shy and secretive night hunters, they search out geckos, skinks and grasshoppers and kill by constriction. A passing resemblance to the viper is thought to work as a defence. We found the snake in the more open southern part of Collserola, an area of grass, shrubs and scattered trees, a summer hunting ground for Short toed eagles.

At the opposite end of the park, not far from a spring, this dragonfly was captured clinging to a bush. I’d have described it as red, till I got home and saw its range of fairground colours: a horse from a devil’s carousel. The rows of spikes on the legs are impressive, ensuring a firm grip on prey. The dimensions of its eyes immediately suggest extraordinary powers of vision.

When identifying the dragonfly, the yellow stripe along the length of the legs pointed me to the Common darter (Sympetrum striolatum), which was confirmed when Sue put her shots up on the forum.

Finally, in the centre of Collserola, the most disturbed and built-up part, this creature was rescued from a busy track. A convoy of cars was driving away from a restaurant, coating us and everything around in dust. The Eyed hawk moth caterpillar (Smerinthus ocellata) was carried to a safer place on a notebook, hence the garish studio background for its portrait.

The caterpillar has a distinguishing blue horn, slanting white stripes (7 in all) and red spiracles (breathing holes).

It was cold at nearly 2,600m, but there were plenty of grassy hollows and boulders to shelter from the wind. The Port de Ratera was created when ice overflowed from the Ratera basin into the Saboredo. This colossal polishing has created a natural resting place, appreciated by walkers, whether approaching via the scree slopes from the Refugio d’Amitges, or climbing up from Val d’Aran.

The route from the Sant Maurici lake, the GR 11, rises in a series of giant steps, a typical pattern of glacial erosion in hard granitic rock. For the walker this translates as tough slogs interspersed with welcome respites.

On one of these pauses, among still water and scattered rocks, a herd of chamois (Rupicapra pyrenaica) were foraging, a group of females and young. Separated from the rest, one of the adults came bounding past, hooves thudding as it circled the valley.

The renewed silence was broken by a piercing whistle, as if a referee had just stopped play. The first time I ever heard a marmot’s warning call, I was sure it was a bird. One tone warns of raptors and another of danger on the ground. The Pyrenean marmots didn’t survive the last ice age, but were re-introduced in 1948, and have been burrowing there extensively ever since. They are Europe’s largest and perhaps shaggiest rodents, preferring to stay underground on hot days, as well as hibernating throughout winter. This upright marmot was on lookout duty.

Black redstarts were ubiquitous at all levels, from the streets of Espot to the top of the pass. They’re also a familiar sight at sea level, visiting Barcelona in winter. Other birds I saw that day were rock bunting, wheatear and alpine accentor, and a solitary mallard in the Estanyet de Port de Ratera.

Near the pass I found Globe-headed rampion (Phyteuma hemisphaericum), which grows in the highest reaches of the park, up to 3,000m, thriving in thin sandy soils. Starry saxifrage (Saxifraga stellaris) was in flower by a stream.

Another resilient high altitude species is the Mountain pine (Pinus uncinata). One grows near the pass, braced against the prevailing north-west wind. Another, on the south side of Els Encantats at 2,700m, is a candidate for the highest tree of Spain. Bark blending into stone, they are capable of growing out of a fissured rock.

Presiding over the Sant Maurici lake, this vast two-peaked monolith is omnipresent in local hikes - a yardstick to measure how far you’ve walked and how high you’ve reached.

In the legend of Els Encantats, two hunters were enticed onto the mountain by the biggest chamois they’d ever seen, and then blasted by lightening for daring to mock the good villagers at mass in Sant Maurici’s chapel. Their fossilised remains, two splinters of rock, can be seen between the peaks.

Everywhere there are bleached, twisted wrecks of trees, another reminder of the dangers of lightning. With afternoon storms forecast, I didn’t aim to go far. The day had started misty and still, but seemingly from nowhere, waves of wind began searing through the crags. Suddenly the sky was an electric blue, and my hands were frozen. Clouds were surging past, and over the shoulders of Els Encantats a cumulo-nimbus was rising. Enhancing the vividness of the moment, a stunning tangerine-coloured butterfly was browsing at the shore of the Sant Maurici lake: a Scarce copper (Lycaena virgaureae).

I climbed up to a spot protected from the wind, with the whole majestic block of Els Encantats in view - from the peaks, with the doomed hunters inbetween, to the creamy-white glaciar in its belly button - a vestige of the 400m-deep glacier that once filled the Escrita valley.

I could see silver glitter racing across the Estany de Sant Maurici in the valley bottom, the water a deep turquoise compared to the dark blue of higher lakes, which lack sediments, minerals and algae. I was watching a flock of crossbills prise open pine cones but the sky beyond the great mountain was now the darkest blue - time to go.

Further up, the path narrows, and you reach the Estany de les Obagues de Ratera (the Lake on the dark side of the Ratera). Red and white poles stop you getting lost, so the map could’ve stayed folded, but once open, a tempting alternative materialised, leading away from the GR 11 up to some tiny lakes.

The contrast with the previous day was brutal. The way was marked by cairns, to guide you over an avalanche of rocks. Going became a little easier as the path crept along a narrow strip of grass skirting a vertical wall. There were traces of chamois everywhere. What took me half an hour of awkward balancing they could skip across in 3 minutes. There was no sign of any lakes.

I reached an outcrop of Mountain pines (Pinus uncinata) and sat in their shade, as if for protection. Unsoftened by vegetation or water, this was the harsh side of the mountains. The dead silence was broken by the cawing of a raven.

Back at the Estany de Obagues de Ratera, I noticed a round white spot in a crevice: a dipper (Cinclus cinclus). Scouting around the streams I found some late pink and white orchids (see discussion on forum). There were also Field gentians (Gentianella campestris), discrete but welcome flowers at the end of summer. Small details, but very reassuring after the stark wilderness higher up.

This time I kept to the GR 11, but in the other direction. Instead of taking one of the jeep taxis that wait on the hour at the Sant Maurici lake, I walked back to Espot. The path follows the sunny side of the Escrita river, through meadows and tunnels of hazlenut trees. The dark side is covered by a thick mass of uniform fir forest haunted by capercaillies. The setting sun escaped from the clouds, lighting up the valley and the leaf flurries shed by silver birches. Long shadows were cast eastwards towards the mountains of Andorra.

The way was unsignposted but quite well marked by cairns, and I only strayed twice, where the path branched. After a summer in sandals, I felt clumsy in heavy boots, stumbling over the rocks and gasping from the sheer steepness.

The path wound through a knot of Mountain pines and dense alpenrose, emerging onto a small plateau. It was a resting place for a narrow river that had just finished cascading down a cliff. It now paused to meander peacefully among grass and flowers, before resuming its turbulent course, crashing down into the Ratera lake, as the Cascada de la Ratera.

It was an arcadian scene at an altitude of 2,200 m. The water was crystal clear. Orange fritillaries floated among heather and harebells still glistening with rain drops after last night’s storm. The distant roar from the waterfall faded in and out with the gusts of wind. A one-horned chamois (Rupicapra pyrenaica) foraged among the boulders on the other side, unperturbed as long as I kept my distance. Perhaps it had found a patch of alpine clover, with its delicious liquorice-flavoured roots.

After some false starts, I located the path on the other side of the stream, and more steep climbing took me to a cluster of small lakes. Tiny frogs clung to stalks of grass, among white starry flowers. Unexpected murmurs came from the rocks, where water trickled unseen.

Besides its proliferation of lakes (272 in all), the park is also renowned for the splintered crests of its mountains, a myriad of crags and needles, the result of freeze-thaw action. The roving clouds fragment the mountains even more, as the sun selectively illuminates a peak or picks out a crevasse. Highly sculpted, yet never static, it’s a landscape that is renewed with every step you take.

I also appreciated the park’s capacity for regeneration in another sense. It bears the weight of visitors lightly - you wouldn’t guess it had just emerged from the busiest month of the year. In the peace of that day, a weathered clothes tag found by a rock, “Boreal UK”, seemed it was lost a decade ago.

In such surroundings, and with so much new flora and fauna to take in, you enter a different time dynamic, disassociated with your watch. I could hardly believe the time - mid-afternoon and, although the Refugio d’Amitges was in sight, the Port de Ratera was still a long way off. I’d try again the following day.

For Espot is essentially a place for practicalities, somewhere to find food and a bed: a good base for exploring the Aigüestortes and Sant Maurici National Park. It was only after three days, when a storm chased me down early from the heights, that I went to look around.

The river Escrita runs west to east and divides the village into Espot Solau (sunny) and Espot Obago (shady). The Solau is the flatter side- it’s where the wealthier villagers established their homes in the past. There’s the usual smattering of cranes as apartments go up. A new complex advertises “the privilege of living in the Solau”. You too can have your place in the sun.

But there’s still a meadow, recently mowed, and the old slate roofs have rustied over with a moss that glows mustard yellow in the sun.

Over on the shady side, the houses shelter close together on steep and narrow streets. Cats slip through gaps under wooden doors. Near the top, sheep were bleating inside a barn. Stone, slate and wood, and the occasional boulder, are the building materials.

After the downpour, children, supervised by their grandmothers, were back out playing, and birds had resumed their activities. In Espot Solau, there was a constant traffic of swallows flying in and out of a half-restored barn. A bunch of young Crag martins (Ptyonoprogne rupestris) perched on the end of a wooden beam.

They exercised their wings, took short flights and begged - off each other as much as their parents.

One grew tired of throat-wobbling and yakking, and crash-landed through the branches into the flamingo enclosure. The lion pen, fortunately, is quite far away. Dark and dishevelled, as if it had come through a chimney, it explored the area, not entirely sure where it was going. A more mature juvenile, sleek in morning suit-grey, exhibited the next stage of plumage in young herons.

The keeper arrived with a container of live goldfish, which he freed into the pelicans’ moat. It’s one way of stirring the hefty birds into action. They enthusiastically set about catching their lunch, casting their expandable bills sideways under water, like fishing nets. And there was plenty left for egrets and herons to practice their fishing skills too, deploying quite different strategies: the egrets would run after their prey, poised to change direction in an instant, while the herons relied on their long sinuous necks to snatch the fleeing fish. Owners of ornamental garden ponds would have had to look away.

As they live directly underneath the heronry, and share a fish diet, the pelicans are the captives most affected by its spectacular expansion. But although their placid existence has been disrupted, this year a pelican chick was successfully hatched, a rare occurrence in the zoo.

The one-footed Malibu stork that used to share the enclosure was immediately transferred elsewhere. A tough, powerfully-billed old warrior, it would brazen it out with the herons at their most competitive, while the pelicans, overwhelmed, huddled in a corner.

The baby pelican has grown into a vast fleecy lump that spends its life on a pedestal, being fed by doting parents. It appeared quite capable of looking after itself, lunging at one of the herons when it came too near. The startled heron waited till the chick had dozed off before approaching again, seeking out any forgotten fish.

Pelicans, herons and egrets, all were in moult, with feathers sticking out at odd angles, waiting to fall. The pelicans were like shabby old eiderdowns, shedding clouds of feathers. The plane tree leaves were also drifting down, and soon the empty nests will be visible again.

In the narrow valley of Sant Just, sounds carry far. The whack of tennis balls on the courts under the radio transmitter of Sant Pere Màrtir is distinctly heard on the other side. This late August evening a flock of around 50 bee-eaters (Merops apiaster) fill it with their distinctive calls. They’ve congregated to feed on the insects that have risen in frenzied columns after the rain. Insubstantial fare compared to their habitual prey, bees or dragonflies, which are picked off one by one from a vantage point, but available in industrial quantities.

Unlike the swifts, who maintain an intense silence when hunting, bee-eaters communicate constantly. They glide and flutter, with acrobatic flourishes, adding tropical colour to the dried-out end-of-summer valley. I’d love to have included a photograph of their turquoise breasts, their sharply pointed wings and tails, but none came out. However, their whirling supper was impossible to miss.

The first rain in a month has also drawn out scents, dampened the dust, washed off the leaves. In the last phase of summer, one of the few plants in flower is fennel (Foeniculum vulgare), grown tall and wiry, covering the hillsides in delicate yellow filigree. The animal scats along the way are packed with seeds and remains of berries. The path is littered with gnawed pine cones – the culprit, a red squirrel (Sciurus vulgaris), gives itself away by shaking a branch overhead.

There’s not much daylight left when the bee-eaters withdraw, their calls gradually getting fainter. Alpine swifts plunge down the valley after them in a whoosh of strength. Soon it’ll be the bats’ turn to feast.

As I’m climbing up to Sant Pere Màrtir, the final outpost of the Collersola massif, the sun slips behind a cloud and then the horizon. I’m shocked to see it’s only 8.30pm - an hour of daylight has been docked since I was last up here. The low grey clouds are tinged violet, and eventually orange, as the city lights come on. Far below, the motorways are strung with golden beads, as cars pour into the city. Many people will be returning from their summer holidays.

I follow the ridge back to Vallvidrera in the dusk, bats flickering close to my head, and the pulsing crickets gaining volume. A family of boars is investigating the car park mirador. A deep grunt and they trot on, followed after a while by a tiny figure, scampering as fast as it can for fear of being left behind. This year’s boarlets have yet to experience the marvels of autumn - acorns without limit, softened earth that’s easy to dig, and muddy puddles to wallow in.

Nattily dressed for such a hot day, he was wearing a crisp orange shirt, brown trousers belted high and a blue beret positioned in horizontal perfection. He approached the hoopoe tree but wasn’t interested in the nest. Instead, he held up a tape recorder and recorded the cicadas singing. Satisfied, he played it back and went on his way.

Immediately, a hoopoe nestling peered out of the hole. This second clutch of mid-summer will have grown listening to the relentless orchestra of cicadas - briefly intensified by the man in the blue beret.